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Document and Entity Information - shares	3 Months Ended
Document and Entity Information - shares	Mar. 31, 2020	May 04, 2020
Document And Entity Information
Entity Registrant Name	RIBBON COMMUNICATIONS INC.
Entity Central Index Key	0001708055
Current Fiscal Year End Date	--12-31
Entity Filer Category	Accelerated Filer
Entity Emerging Growth Company	false
Entity Small Business	false
Entity Shell Company	false
Document Type	10-Q
Document Period End Date	Mar. 31, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q1
Amendment Flag	false
Entity Common Stock, Shares Outstanding		144,771,217
Entity Current Reporting Status	Yes

Condensed Consolidated Balance Sheets - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash and cash equivalents	$ 96,830	$ 44,643
Restricted cash	13,238	0
Accounts receivable, net	205,793	192,706
Inventory	67,067	14,800
Other current assets	45,904	27,146
Total current assets	428,832	279,295
Property and equipment, net	46,903	28,976
Intangible assets, net	452,930	213,366
Goodwill	414,389	224,896
Deferred income taxes	6,225	4,959
Operating lease right-of-use assets	66,295	36,654
Other assets	56,915	26,762
Total assets	1,472,489	814,908
Current liabilities:
Current portion of term debt	13,500	2,500
Revolving credit facility	0	8,000
Accounts payable	89,323	31,412
Accrued expenses and other	136,019	56,700
Operating lease liabilities	18,201	7,719
Deferred revenue	113,699	100,406
Total current liabilities	370,742	206,737
Long-term debt, net of current	381,743	45,995
Operating lease liabilities, net of current	55,857	37,202
Deferred revenue, net of current	25,911	20,482
Deferred income taxes	17,443	4,648
Other long-term liabilities	67,089	16,589
Total liabilities	918,785	331,653
Commitments and contingencies (Note 18)
Stockholders' equity:
Preferred stock, $0.01 par value per share; 10,000,000 shares authorized, none issued and outstanding	0	0
Common stock, $0.0001 par value per share; 240,000,000 shares authorized; 144,351,304 shares issued and outstanding at March 31, 2020; 110,471,995 shares issued and outstanding at December 31, 2019	14	11
Additional paid-in capital	1,860,150	1,747,784
Accumulated deficit	(1,300,237)	(1,267,067)
Accumulated other comprehensive (loss) income	(6,223)	2,527
Total stockholders' equity	553,704	483,255
Total liabilities and stockholders' equity	$ 1,472,489	$ 814,908

Condensed Consolidated Balance Sheets (Parenthetical) - $ / shares	Mar. 31, 2020	Dec. 31, 2019
Statement of Financial Position [Abstract]
Preferred stock, par value (in dollars per share)	$ 0.01	$ 0.01
Preferred stock, shares authorized (in shares)	10,000,000	10,000,000
Preferred stock, shares issued (in shares)	0	0
Preferred stock, shares outstanding (in shares)	0	0
Common stock, par value (in dollars per share)	$ 0.0001	$ 0.0001
Common stock, shares authorized (in shares)	240,000,000	240,000,000
Common stock, shares issued (in shares)	144,351,304	110,471,995
Common stock, shares outstanding (in shares)	144,351,304	110,471,995

Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Revenue:
Total revenue	$ 157,982	$ 118,928
Cost of revenue:
Total cost of revenue	76,412	62,339
Gross profit	81,570	56,589
Operating expenses:
Research and development	42,295	35,933
Sales and marketing	36,351	30,059
General and administrative	17,205	18,694
Acquisition- and integration-related	12,384	3,199
Restructuring and related	2,075	4,932
Total operating expenses	110,310	92,817
Loss from operations	(28,740)	(36,228)
Interest expense, net	(3,395)	(1,364)
Other (expense) income, net	(844)	7,774
Loss before income taxes	(32,979)	(29,818)
Income tax provision	(191)	(1,014)
Net loss	$ (33,170)	$ (30,832)
Loss per share:
Basic (in dollars per share)	$ (0.27)	$ (0.29)
Diluted (in dollars per share)	$ (0.27)	$ (0.29)
Weighted average shares used to compute loss per share:
Basic (in shares)	120,992	108,167
Diluted (in shares)	120,992	108,167
Product
Revenue:
Total revenue	$ 75,899	$ 47,480
Cost of revenue:
Total cost of revenue	44,933	33,147
Service
Revenue:
Total revenue	82,083	71,448
Cost of revenue:
Total cost of revenue	$ 31,479	$ 29,192

Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Statement of Comprehensive Income [Abstract]
Net loss	$ (33,170)	$ (30,832)
Other comprehensive income (loss), net of tax:
Unrealized loss on interest rate swap	(9,527)	0
Foreign currency translation adjustments	777	(8)
Unrealized gain on available-for sale marketable securities, net of reclassification adjustments for realized amounts	0	13
Employee retirement benefits	0	32
Other comprehensive (loss) income, net of tax	(8,750)	37
Comprehensive loss	$ (41,920)	$ (30,795)

- Definition

The portion of profit or loss for the period, net of income taxes, which is attributable to the parent.

+ References + Details

Condensed Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common stock	Additional paid-in capital	Accumulated deficit	Accumulated other comprehensive income (loss)	ECI	ECI Common stock	ECI Additional paid-in capital	Anova Data, Inc.	Anova Data, Inc. Common stock	Anova Data, Inc. Additional paid-in capital
Balance (in shares) at Dec. 31, 2018		106,815,636
Balance at Dec. 31, 2018	$ 590,298	$ 11	$ 1,723,576	$ (1,136,992)	$ 3,703
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)		88,354
Exercise of stock options	151		151
Vesting of restricted stock awards and units (in shares)		806,813
Vesting of restricted stock awards and units	0
Vesting of performance-based stock awards (in shares)		9,466
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations (in shares)		(181,428)
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations	(968)		(968)
Shares issued as consideration in connection with acquisition (in shares)										2,948,793
Shares issued as consideration in connection with acquisition									$ 15,186		$ 15,186
Reclassification of liability to equity for bonuses converted to stock	1,052		1,052
Stock-based compensation expense	4,139		4,139
Other comprehensive income (loss)	37				37
Net loss	(30,832)			(30,832)
Balance (in shares) at Mar. 31, 2019		110,487,634
Balance at Mar. 31, 2019	$ 579,063	$ 11	1,743,136	(1,167,824)	3,740
Balance (in shares) at Dec. 31, 2019	110,471,995	110,471,995
Balance at Dec. 31, 2019	$ 483,255	$ 11	1,747,784	(1,267,067)	2,527
Increase (Decrease) in Stockholders' Equity
Exercise of stock options (in shares)	3,014	3,014
Exercise of stock options	$ 5		5
Vesting of restricted stock awards and units (in shares)		1,016,982
Vesting of restricted stock awards and units	0
Vesting of performance-based stock awards (in shares)		315,866
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations (in shares)		(273,104)
Shares of restricted stock returned to the Company under net share settlements to satisfy tax withholding obligations	(792)		(792)
Shares issued as consideration in connection with acquisition (in shares)							32,500,000			316,551
Shares issued as consideration in connection with acquisition						$ 108,550	$ 3	$ 108,547	$ 1,630		$ 1,630
Stock-based compensation expense	2,976		2,976
Other comprehensive income (loss)	(8,750)				(8,750)
Net loss	$ (33,170)			(33,170)
Balance (in shares) at Mar. 31, 2020	144,351,304	144,351,304
Balance at Mar. 31, 2020	$ 553,704	$ 14	$ 1,860,150	$ (1,300,237)	$ (6,223)

Condensed Consolidated Statements of Cash Flows - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Cash flows from operating activities:
Net loss	$ (33,170)	$ (30,832)
Adjustments to reconcile net loss to cash flows provided by operating activities:
Depreciation and amortization of property and equipment	3,474	2,921
Amortization of intangible assets	14,334	11,922
Amortization of debt issuance costs	1,854	88
Stock-based compensation	2,976	4,139
Deferred income taxes	(99)	347
Reduction in deferred purchase consideration	(69)	(8,124)
Foreign currency exchange losses	854	352
Changes in operating assets and liabilities:
Accounts receivable	46,156	53,854
Inventory	4,468	3,692
Other operating assets	(478)	(762)
Accounts payable	(27,029)	(6,999)
Accrued expenses and other long-term liabilities	22,310	(13,095)
Deferred revenue	4,351	2,076
Net cash provided by operating activities	39,932	19,579
Cash flows from investing activities:
Purchases of property and equipment	(6,017)	(3,766)
Business acquisitions, net of cash acquired	(346,852)	0
Maturities of marketable securities	0	5,295
Proceeds from the sale of fixed assets	43,500	0
Net cash (used in) provided by investing activities	(309,369)	1,529
Cash flows from financing activities:
Borrowings under revolving line of credit	0	37,000
Principal payments on revolving line of credit	(8,000)	(35,000)
Proceeds from issuance of term debt	403,500	0
Principal payments of long-term debt	(48,750)	0
Payment of deferred purchase consideration	0	(21,876)
Principal payments of finance leases	(338)	(230)
Payment of debt issuance costs	(10,573)	0
Proceeds from the exercise of stock options	5	151
Payment of tax withholding obligations related to net share settlements of restricted stock awards	(792)	(968)
Net cash provided by (used in) financing activities	335,052	(20,923)
Effect of exchange rate changes on cash, cash equivalents and restricted cash	(190)	59
Net increase in cash, cash equivalents and restricted cash	65,425	244
Cash and cash equivalents, beginning of year	44,643	43,694
Cash, cash equivalents and restricted cash, end of period	110,068	43,938
Supplemental disclosure of cash flow information:
Interest paid	688	831
Income taxes paid	1,259	777
Income tax refunds received	0	100
Supplemental disclosure of non-cash investing activities:
Capital expenditures incurred, but not yet paid	6,300	399
Acquisition purchase consideration - deferred payments	0	1,700
Shares of common stock issued as purchase consideration	110,180	15,186
Supplemental disclosure of non-cash financing activities:
Total fair value of restricted stock awards, restricted stock units and performance-based stock units on date vested	$ 3,182	$ 4,334

BASIS OF PRESENTATION	3 Months Ended
BASIS OF PRESENTATION	Mar. 31, 2020
Accounting Policies [Abstract]
BASIS OF PRESENTATION	BASIS OF PRESENTATION Business Ribbon is a leading provider of next generation software solutions to telecommunications, wireless and cable service providers and enterprises of all sizes across industry verticals. With the March 3, 2020 completion of the merger with ECI Telecom Group Ltd ("ECI"), Ribbon now also provides optical and packet networking products and software-defined solutions to service providers and critical infrastructure sectors like utilities, government and defense. With over 1,000 customers around the globe, including some of the largest telecommunications service providers, enterprises and utilities in the world, Ribbon enables its customers to evolve and modernize their communications networks and packet optical networking infrastructures through software and hardware. By securing and enabling reliable and scalable Internet Protocol ("IP") and packet optical networks and applications, Ribbon helps its customers adopt the next generation of software-, cloud- and edge-based technologies to drive new, incremental revenue, while protecting their existing revenue streams. Ribbon's software solutions provide a secure way for its customers to connect and leverage multivendor, multiprotocol communications systems and applications across their networks and the cloud in a rapidly changing ecosystem of IP-enabled devices, such as smartphones and tablets. In addition, Ribbon's software solutions secure cloud-based delivery of unified communications ("UC") solutions - both for service providers transforming to a cloud-based network and for enterprises using cloud-based UC - and support the increasing demand on network infrastructure created by ongoing IP traffic growth and the forecast demand and build-outs to be created by increased traffic from 5G applications and devices. Ribbon sells its products and solutions through both direct sales and indirect channels, leveraging the assistance of resellers, and provides ongoing support to its customers through a global services team with experience in design, deployment and maintenance of some of the world's largest software IP networks. Basis of Presentation In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting only of normal recurring items, necessary for their fair presentation with accounting principles generally accepted in the United States of America ("GAAP") and with the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). On March 3, 2020 (the "ECI Merger Date"), the Company merged with ECI Telecom Group Ltd. ("ECI") (the "ECI Merger"). The financial results of ECI are included in the Company's condensed consolidated financial statements for the period subsequent to the ECI Merger Date. On February 28, 2019 (the "Anova Acquisition Date"), the Company acquired the business and technology assets of Anova Data, Inc. ("Anova"). The financial results of Anova are included in the Company's condensed consolidated financial statements for the period subsequent to the Anova Acquisition Date. Interim results are not necessarily indicative of results for a full year or any future interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2019 (the "Annual Report"), which was filed with the SEC on February 28, 2020. Significant Accounting Policies The Company's significant accounting policies are disclosed in Note 2 to the Consolidated Financial Statements included in the Annual Report. There were no material changes to the significant accounting policies during the three months ended March 31, 2020, with the exception of policies on transfers of financial assets and warranty costs: Transfers of Financial Assets. The Company's recently acquired subsidiary, ECI Telecom Group Ltd. ("ECI"), maintains customer receivables factoring agreements with a number of financial institutions. Under the terms of these agreements, the Company may transfer receivables to the financial institutions, on a non-recourse basis, provided that the financial institutions approve the receivables in advance. The Company maintains credit insurance policies from major insurance providers or obtains letters of credit from the customers for a majority of its factored trade receivables. In some cases, the Company maintains some recourse obligations, limited to events of commercial disputes, such as product defects, which are not covered under the credit insurance policy, and are unrelated to the credit worthiness of the customer. The Company does not expect any recourse to take place in the foreseeable future due to commercial disputes. The Company accounts for the factoring of its financial assets as a sale of the assets and records the factoring fees, when incurred, as a component of interest expense in the condensed consolidated statements of operations and the proceeds from the sales of receivables are included in cash from operating activities in the condensed consolidated statements of cash flows. During the three months ended March 31, 2020, the Company received $15.1 million of cash from the sale of certain accounts receivable and recorded $0.1 million of interest expense in connection with these transactions. Warranty. The Company records warranty liabilities for estimated costs of fulfilling its obligations under standard limited hardware and software warranties at the time of sale. The liability for standard warranties is included in Accrued expenses and other and Other non-current liabilities in the condensed consolidated balance sheet at March 31, 2020. The specific warranty terms and conditions vary depending upon the country in which the Company does business, but generally includes material costs, technical support, labor and associated overhead over a period ranging from one to three years. The Company's liability for product warranties was $15.7 million, of which $6.7 million was current and included in Accrued expenses and other and $9.0 million was long-term and included in Other long-term liabilities in the Company's condensed consolidated balance sheet at March 31, 2020. The Company did not have a warranty accrual at December 31, 2019. Principles of Consolidation The condensed consolidated financial statements include the accounts of Ribbon and its wholly-owned subsidiaries. Intercompany transactions and balances have been eliminated in consolidation. Use of Estimates and Judgments The preparation of financial statements in conformity with GAAP requires Ribbon to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and judgments relied upon in preparing these condensed consolidated financial statements include accounting for business combinations, revenue recognition for multiple element arrangements, inventory valuations, assumptions used to determine the fair value of stock-based compensation, intangible asset and goodwill valuations, including impairments, legal contingencies and recoverability of Ribbon's net deferred tax assets and the related valuation allowances. Ribbon regularly assesses these estimates and records changes in estimates in the period in which they become known. Ribbon bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. Actual results could differ from those estimates. Reclassifications Certain reclassifications, not affecting previously reported net loss, have been made to the previously issued financial statements to conform to the current period presentation. Restricted Cash The Company classifies as restricted cash all cash pledged as collateral to secure long-term obligations and all cash whose use is otherwise limited by contractual provisions. At March 31, 2020, the Company had $13.2 million of restricted cash, comprised of $8.4 million restricted in connection with a tax payment on certain fixed assets formerly held by ECI that were sold in connection with the ECI Merger, and $4.8 million restricted short-term bank deposits pledged to secure certain performance and financial bonds as security for the Company's obligations under tenders, contracts and to one of its main subcontractors. Fair Value of Financial Instruments The carrying amounts of the Company's financial instruments approximate their fair values and include cash equivalents, accounts receivable, borrowings under a revolving credit facility, accounts payable and long-term debt. Operating Segments The Company currently operates in a single segment, as the chief operating decision maker made decisions and assessed performance at the company level. The Company's chief operating decision maker is its President and Chief Executive Officer, who began his employment with the Company effective March 1, 2020. From January 1, 2020 to March 1, 2020, the Company's chief operating decision makers were its former Interim Co-Presidents and Chief Executive Officers. Operating segments are identified as components of an enterprise about which separate discrete financial information is utilized for evaluation by the chief operating decision maker in making decisions regarding resource allocation and assessing performance. To date, the chief operating decision maker has made such decisions and assessed performance at the company level as one segment. However, with the acquisition of ECI, the Company's chief operating decision maker is currently assessing the appropriate separate discrete financial information he will utilize for making such decisions. Accordingly, the Company is reporting one operating segment for the three months ended March 31, 2020. Fair Value Hierarchy Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. The three-tier fair value hierarchy is based on the level of independent, objective evidence surrounding the inputs used to measure fair value. A financial instrument's categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The fair value hierarchy is as follows: Level 1. Level 1 applies to assets or liabilities for which there are quoted prices in active markets for identical assets or liabilities. Level 2. Level 2 applies to assets or liabilities for which there are inputs that are directly or indirectly observable in the marketplace, such as quoted prices for similar assets or liabilities in active markets or quoted prices for identical assets or liabilities in markets with insufficient volume or infrequent transactions (less active markets). Level 3. Level 3 applies to assets or liabilities for which there are unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of the assets or liabilities. Recent Accounting Pronouncements The Financial Accounting Standards Board ("FASB") has issued the following accounting pronouncements, all of which became effective for the Company in 2020 and none of which had a material impact on the Company's condensed consolidated financial statements: In March 2020, the FASB issued Accounting Standards Update ("ASU") 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting ("ASU 2020-04"), which provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria that reference LIBOR or another reference rate expected to be discontinued. In March 2020, the FASB issued ASU 2020-03, Codification Improvements to Financial Instruments ("ASU 2020-03"), which makes narrow-scope amendments related to topics regarding fair value option disclosures, applicability of the portfolio exception in Accounting Standards Codification ("ASC") 820 to nonfinancial items, disclosures for depository and lending institutions, cross reference to guidance in ASC 470-50 on line of credit or revolving debt arrangements, cross reference to net asset value practical expedient in ASC 820-10, interaction between ASC 842 and ASC 326 and between ASC 326 and ASC 860-20. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”), which provides guidance on implementation costs incurred in a cloud computing arrangement (“CCA”) that is a service contract. ASU 2018-15 amends ASC 350, Intangibles - Goodwill and Other (“ASC 350”) to include in its scope implementation costs of a CCA that is a service contract and clarifies that a customer should apply the guidance in ASC 350-40 to determine which implementation costs should be capitalized in such a CCA. In August 2018, the FASB issued ASU 2018-14, Compensation - Retirement Benefits - Defined Benefit Plans - General (Subtopic 715-20): Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans (“ASU 2018-14”), which amends ASC 715, Compensation - Retirement Benefits, to add, remove and clarify disclosure requirements related to defined benefit pension and other postretirement plans. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), which changes the fair value measurement requirements of ASC 820, Fair Value Measurement. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), which adds an impairment model that is based on expected losses rather than incurred losses. Under ASU 2016-13, an entity recognizes as an allowance its estimate of expected credit losses, which the FASB believes will result in more timely recognition of such losses. In April and May 2019, the FASB issued ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments - Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments ("ASU 2019-04") and ASU 2019-05 Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief ("ASU 2019-05"), respectively. ASU 2019-04 provides transition relief for entities adopting ASU 2016-13 and ASU 2019-05 clarifies certain aspects of the accounting for credit losses, hedging activities and financial instruments in connection with the adoption of ASU 2016-13. The FASB has issued the following accounting pronouncement which becomes effective for the Company in 2021, which the Company does not believe will have a material impact on its condensed consolidated financial statements upon adoption: In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes ("ASU 2019-12"), which modifies ASC 740 to simplify the accounting for income taxes. ASU 2019-12 addresses the accounting for hybrid tax regimes, tax basis step-up in goodwill obtained in a transaction that is not a business combination, separate financial statements of legal entities not subject to tax, intraperiod tax allocation exception to incremental approach, ownership changes in investments - changes from a subsidiary to an equity method investment, ownership changes in investments - changes from an equity method investment to a subsidiary, interim period accounting for enacted changes in tax law and year-to-date loss limitation in interim period tax accounting.

BUSINESS ACQUISITIONS

3 Months Ended

Mar. 31, 2020

Business Combinations [Abstract]

BUSINESS ACQUISITIONS

ECI

On the ECI Merger Date, Ribbon completed its previously announced merger transaction with ECI in accordance with the terms of the Agreement and Plan of Merger, dated as of November 14, 2019, by and among Ribbon, ECI, an indirect wholly-owned subsidiary of Ribbon ("Merger Sub"), Ribbon Communications Israel Ltd. and ECI Holding (Hungary) kft, pursuant to which Merger Sub merged with and into ECI, with ECI surviving such merger as a wholly-owned subsidiary of Ribbon. Prior to the ECI Merger Date, ECI was a privately-held global provider of end-to-end packet-optical transport and software-defined networking ("SDN") and network function virtualization ("NFV") solutions for service providers, enterprises and data center operators. Ribbon believes the ECI Merger positions the Company for growth and enhances its competitive strengths by expanding its product portfolio beyond solutions primarily supporting voice applications to include data applications and optical networking.

As consideration for the ECI Merger, Ribbon issued the ECI shareholders and certain others 32.5 million shares of Ribbon common stock with a fair value of $108.6 million (the "Stock Consideration") and paid $322.5 million of cash, comprised of $183.3 million to repay ECI's outstanding debt, including both principal and interest, and $139.2 million paid to ECI's selling shareholders (the "Cash Consideration"). In addition, ECI shareholders received $33.4 million from the sale of certain of ECI's real estate assets. Cash Consideration was financed through cash on hand and committed debt financing consisting of a new $400 million term loan facility (the "2020 Term Loan") and new $100 million revolving credit facility (together, the "2020 Credit Facility"), which was undrawn at the ECI Merger Date.

The ECI Merger has been accounted for as a business combination and the financial results of ECI have been included in the Company's condensed consolidated financial statements for the period subsequent to the ECI Merger. The Company's financial results for the three months ended March 31, 2020 include $30.0 million of revenue and $3.3 million of net loss attributable to ECI for the period subsequent to the ECI Merger Date.

As of March 31, 2020, the valuation of acquired assets, identifiable intangible assets and certain assumed liabilities was preliminary. The Company is continuing the process of investigating the facts and circumstances existing as of the ECI Merger Date in order to finalize its valuation. Included in the additional work required to finalize the valuation of assets acquired and liabilities assumed, the Company is assessing the impact of the COVID-19 pandemic on the estimated future revenue and cash flows. This assessment could result in significant changes between the preliminary valuations of the individual identifiable intangible assets and goodwill. The Company expects to finalize the valuation of the assets acquired and liabilities assumed by the first quarter of 2021.

A summary of the preliminary allocation of the purchase consideration for ECI is as follow (in thousands):



Fair value of consideration transferred:
Cash consideration:
Repayment of ECI outstanding debt obligations	$	183,266
Cash paid to selling shareholders	139,244
Payment to selling shareholders from sale of ECI real estate assets	33,400
Less cash and restricted cash acquired	(9,058		)
Net cash consideration	346,852
Fair value of Ribbon stock issued	108,550
Fair value of total consideration	$	455,402

Fair value of assets acquired and liabilities assumed:
Current assets, net of cash and restricted cash acquired	$	131,447
Property and equipment	55,207
Intangible assets:
In-process research and development	31,000
Developed technology	106,900
Customer relationships	114,000
Trade names	2,000
Goodwill	189,493
Other noncurrent assets	56,204
Deferred revenue	(7,731		)
Other current liabilities	(143,873		)
Deferred revenue, net of current	(6,641		)
Deferred tax liability	(13,308		)
Other long-term liabilities	(59,296		)
	$	455,402

The preliminary allocation of purchase consideration to the fair value of assets acquired and liabilities assumed includes a noncurrent asset of $5.7 million, which represents an indemnification receivable from ECI's selling shareholders for certain liabilities for uncertain tax positions in accordance with the Agreement and Plan of Merger.

The Company is still evaluating the fair value of acquired assets and assumed liabilities, the values of which may be subject to change based on the finalization of their respective fair values. The valuation of the acquired intangible assets is inherently subjective and relies on significant unobservable inputs. The Company used an income approach to value the acquired in-process research and development, developed technology, customer relationships and trade name intangible assets. The Company is still evaluating the forecast and the value of these assets could change materially as the Company finalizes the forecast and other inputs used to value these assets. The valuation for each of these intangible assets was based on estimated projections of expected cash flows to be generated by the assets, discounted to the present value at discount rates commensurate with perceived risk. The valuation assumptions take into consideration the Company's estimates of customer attrition, technology obsolescence and revenue growth projections. The Company is amortizing the identifiable intangible assets arising from the ECI Merger in relation to the expected cash flows from the individual intangible assets over their respective useful lives, which have a weighted average life of 12.44 years (see Note 5). Goodwill results from assets that are not separately identifiable as part of the transaction and is not deductible for tax purposes.

Pro Forma Results

The following unaudited pro forma information presents the condensed combined results of operations of Ribbon and ECI for the three months ended March 31, 2020 and 2019 as if the ECI Merger had been completed on January 1, 2019, with adjustments to give effect to pro forma events that are directly attributable to the ECI Merger. These pro forma adjustments include an increase in research and development expense related to the conformance of ECI's cost capitalization policy to Ribbon's, additional amortization expense for the acquired identifiable intangible assets, a decrease in historical ECI interest expense reflecting the extinguishment of certain of ECI's debt as a result of the ECI Merger, and an increase in interest expense reflecting the new debt entered into by the Company in connection with the ECI Merger. Pro forma adjustments also include the elimination of acquisition- and integration-related costs directly attributable to the acquisition from the three months ended March 31, 2020 and inclusion of such costs in the three months ended March 31, 2019.

The unaudited pro forma results do not reflect any operating efficiencies or potential cost savings that may result from the consolidation of the operations of Ribbon and ECI. Accordingly, these unaudited pro forma results are presented for illustrative purposes and are not intended to represent or be indicative of the actual results of operations of the combined company that would have been achieved had the ECI Merger occurred at January 1, 2019, nor are they intended to represent or be indicative of future results of operations (in thousands, except per share amounts):



	Three months ended
	March 31, 2020			March 31, 2019
Revenue	$	183,189		$	208,947
Net loss	$	(39,129	)	$	(63,699	)
Loss per share	$	(0.25	)	$	(0.45	)

Anova Data, Inc.

On the Anova Acquisition Date, the Company acquired the business and technology assets of Anova, a private company headquartered in Westford, Massachusetts that provides advanced analytics solutions (the "Anova Acquisition"). The Anova Acquisition was completed in accordance with the terms and conditions of an asset purchase agreement, dated as of January 31, 2019 (the "Anova Asset Purchase Agreement"). As consideration for the Anova Acquisition, Ribbon issued 2.9 million shares of Ribbon common stock with a fair value of $15.2 million to Anova's sellers and equity holders on the Anova Acquisition Date and held back an additional 330,000 shares with a fair value of $1.7 million (the "Anova Deferred Consideration"), of which 316,551 shares were issued after post-closing adjustments on March 4, 2020. The Anova Deferred Consideration was included as a component of Accrued expenses and other current liabilities in the Company's condensed consolidated balance sheet at December 31, 2019.

The Anova Acquisition was accounted for as a business combination and the financial results of Anova have been included in the Company's condensed consolidated financial statements for the period subsequent to the Anova Acquisition Date. The results for the three months ended March 31, 2019 were not significant to the Company's condensed consolidated financial statements and accordingly, the Company has not provided pro forma financial information. As of March 31, 2020, the valuation of acquired assets, identifiable intangible assets and assumed liabilities was final, as the Company finalized the valuation of the assets acquired and liabilities assumed in the fourth quarter of 2019. The purchase consideration aggregating $16.9 million was allocated to $11.2 million of identifiable intangible assets with a weighted average life of 6.25 years (see Note 5) and working capital items aggregating $0.1 million of net assets acquired. The remaining unallocated amount of $5.5 million was recorded as goodwill. The goodwill is deductible for tax purposes.

Acquisition- and Integration-Related Expenses

Acquisition- and integration-related expenses include those expenses related to acquisitions that would otherwise not have been incurred by the Company, including professional and services fees such as legal, audit, consulting, paying agent and other fees. These amounts include costs related to prior acquisitions, as well as nominal amounts related to acquisitive activities. Integration-related expenses represent incremental costs related to combining the Company and its business acquisitions, such as third-party consulting and other third-party services related to merging previously separate companies' systems and processes. The acquisition-related costs in the three months ended March 31, 2020 primarily relate to the ECI Merger; the acquisition-related costs in the three months ended March 31, 2019 primarily relate to the Anova Acquisition.

The Company's acquisition- and integration-related expenses for the three months ended March 31, 2020 and 2019 were as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019
Professional and services fees (acquisition-related)	$	12,374	$	1,505
Integration-related expenses	10		1,694
	$	12,384	$	3,199

EARNINGS (LOSS) PER SHARE

3 Months Ended

Mar. 31, 2020

Earnings Per Share [Abstract]

EARNINGS (LOSS) PER SHARE

Basic earnings (loss) per share is computed by dividing net income (loss) by the weighted average number of shares outstanding during the period. For periods in which the Company reports net income, diluted net earnings per share is determined by using the weighted average number of common and dilutive common equivalent shares outstanding during the period unless the effect is antidilutive.

The calculations of shares used to compute earnings (loss) per share were as follows (in thousands):



	Three months ended
	March 31, 2020	March 31, 2019
Weighted average shares outstanding—basic	120,992	108,167
Potential dilutive common shares	—	—
Weighted average shares outstanding—diluted	120,992	108,167

Options to purchase the Company's common stock and unvested shares of restricted and performance-based stock and stock units aggregating 11.7 million shares have not been included in the computation of diluted loss per share for the three months ended March 31, 2020 because their effect would have been antidilutive. Options to purchase the Company's common stock, unvested shares of restricted and performance-based stock and stock units, and shares in connection with future purchases under the Company's Amended and Restated 2000 Employee Stock Purchase Plan, as amended (the "ESPP"), aggregating 4.5 million shares have not been included in the computation of diluted loss per share for the three months ended March 31, 2019 because their effect would have been antidilutive.

INVENTORY

3 Months Ended

Mar. 31, 2020

Inventory Disclosure [Abstract]

INVENTORY

Inventory at March 31, 2020 and December 31, 2019 consisted of the following (in thousands):



	March 31, 2020			December 31, 2019
On-hand final assemblies and finished goods inventories	$	71,964		$	13,283
Deferred cost of goods sold	4,167			2,441
	76,131			15,724
Less noncurrent portion (included in other assets)	(9,064		)	(924		)
Current portion	$	67,067		$	14,800

INTANGIBLE ASSETS AND GOODWILL

3 Months Ended

Mar. 31, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

INTANGIBLE ASSETS AND GOODWILL

The Company's intangible assets at March 31, 2020 and December 31, 2019 consisted of the following (in thousands):



March 31, 2020	Weighted average amortization period (years)	Cost		Accumulated amortization		Net carrying value
In-process research and development	*	$	36,600	$	—	$	36,600
Developed technology	7.92	295,780		109,714		186,066
Customer relationships	11.83	266,140		38,507		227,633
Trade names	3.60	4,000		1,369		2,631
Internal use software	3.00	730		730		—
	9.13	$	603,250	$	150,320	$	452,930



December 31, 2019	Weighted average amortization period (years)	Cost		Accumulated amortization		Net carrying value
In-process research and development	*	$	5,600	$	—	$	5,600
Developed technology	6.79	188,880		100,760		88,120
Customer relationships	9.46	152,140		33,350		118,790
Trade names	5.20	2,000		1,144		856
Internal use software	3.00	730		730		—
	7.82	$	349,350	$	135,984	$	213,366

* An in-process research and development intangible asset has an indefinite life until the product is generally available, at which time such asset is typically reclassified to developed technology.

Amortization expense for intangible assets for the three months ended March 31, 2020 and 2019 was as follows (in thousands):



	Three months ended				Statement of operations classification
	March 31, 2020		March 31, 2019		Statement of operations classification
Developed technology	$	8,954	$	9,645	Cost of revenue - product
Customer relationships	5,156		2,130		Sales and marketing
Trade names	224		147		Sales and marketing
	$	14,334	$	11,922

Estimated future amortization expense for the Company's intangible assets at March 31, 2020 was as follows (in thousands):



Years ending December 31,
Remainder of 2020	$	44,869
2021	64,323
2022	58,153
2023	51,445
2024	43,477
Thereafter	190,663
	$	452,930

The changes in the carrying value of the Company's goodwill in the three months ended March 31, 2020 and 2019 were as follows (in thousands):




Balance at January 1	2020			2019
Goodwill	$	392,302		$	386,761
Accumulated impairment losses	(167,406		)	(3,106		)
	224,896			383,655
Acquisition of ECI	189,493			—
Acquisition of Anova	—			5,541
Balance at March 31	$	414,389		$	389,196

Balance at March 31
Goodwill	$	581,795		$	392,302
Accumulated impairment losses	(167,406		)	(3,106		)
	$	414,389		$	389,196

ACCRUED EXPENSES

3 Months Ended

Mar. 31, 2020

Payables and Accruals [Abstract]

ACCRUED EXPENSES

Accrued expenses at March 31, 2020 and December 31, 2019 consisted of the following (in thousands):



	March 31, 2020		December 31, 2019
Employee compensation and related costs	$	51,718	$	27,166
Professional fees	12,875		13,331
Taxes payable	18,424		842
Other	53,002		15,361
	$	136,019	$	56,700

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES

3 Months Ended

Mar. 31, 2020

Restructuring and Related Activities [Abstract]

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES

The Company recorded restructuring and related expense aggregating $2.1 million and $4.9 million in the three months ended March 31, 2020 and 2019, respectively. Restructuring and related expense includes both restructuring expense (primarily severance and related costs), estimated future variable lease costs for vacated properties with no intent or ability of sublease, and accelerated rent amortization expense.

For restructuring events that involve lease assets and liabilities, the Company applies lease reassessment and modification guidance and evaluates the right-of-use assets for potential impairment. If the Company plans to exit all or distinct portions of a facility and does not have the ability or intent to sublease, the Company will accelerate the amortization of each of those lease components through the vacate date. The accelerated amortization is recorded as a component of Restructuring and related expense in the Company's condensed consolidated statements of operations. Related variable lease expenses will continue to be expensed as incurred through the vacate date, at which time the Company will reassess the liability balance to ensure it appropriately reflects the remaining liability associated with the premises and record a liability for the estimated future variable lease costs.

The components of Restructuring and related expense for the three months ended March 31, 2020 and 2019 were as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019
Severance and related costs	$	1,771	$	4,919
Variable and other facilities-related costs	234		13
Accelerated amortization of lease assets due to cease-use	70		—
	$	2,075	$	4,932

ECI Executive Severance

In connection with the ECI Merger, the Company is releasing three former executives of ECI and recorded $1.1 million of restructuring and related expense for severance for these individuals in accordance with their respective employment and related agreements in the three months ended March 31, 2020. At March 31, 2020, these amounts had not yet been paid. The Company expects these amounts will be paid by the end of 2020.

2019 Restructuring and Facilities Consolidation Initiative

In June 2019, the Company implemented a restructuring plan to further streamline the Company's global footprint, improve its operations and enhance its customer delivery (the "2019 Restructuring Initiative"). The 2019 Restructuring Initiative includes facility consolidations, refinement of the Company's research and development activities, and a reduction in workforce. In connection with this initiative, the Company expects to reduce its focus on hardware and appliance-based development over time and to increase its development focus on software virtualization, functional simplicity and important customer requirements. The facility consolidations under the 2019 Restructuring Initiative (the "Facilities Initiative") include a consolidation of the Company's North Texas sites into a single campus, housing engineering, customer training and support, and administrative functions, as well as a reduction or elimination of certain excess and duplicative facilities worldwide. In addition, the Company intends to substantially consolidate its global software laboratories and server farms into two lower cost North American sites. The Company continues to evaluate its properties included in the Facilities Initiative for accelerated amortization and/or right-of-use asset impairment. The Company expects that the actions under the Facilities Initiative will be completed by the end of 2020.

In connection with the 2019 Restructuring Initiative, the Company recorded restructuring expense and related expense of $1.0 million in the three months ended March 31, 2020, comprised of $0.7 million for severance and related costs for five employees and $0.3 million related to facilities. The Company expects that it will record nominal additional Restructuring and related expense related to severance and related costs under the 2019 Restructuring Initiative. A summary of the 2019 Restructuring Initiative accrual activity for severance and related costs for the three months ended March 31, 2020 is as follows (in thousands):



	Balance at January 1, 2020		Initiatives charged to expense		Reclassify accelerated amortization to operating lease liabilities			Cash payments			Balance at March 31, 2020
Severance	$	2,110	$	655	$	—		$	(1,253	)	$	1,512
Facilities	991		304		(70		)	(272		)	953
	$	3,101	$	959	$	(70	)	$	(1,525	)	$	2,465

Accelerated rent amortization is recognized from the date that the Company commences the plan to fully or partially vacate a facility, for which there is no intent or ability to enter into a sublease, through the final vacate date. The accelerated rent amortization recorded in connection with the Facilities Initiative reduced the value of the Company's Operating lease right-of-use assets recorded in the Company's condensed consolidated balance sheets at March 31, 2020 and December 31, 2019, respectively. The liability for the total lease payments for each respective facility is included as a component of Operating lease liabilities in the Company's condensed consolidated balance sheets, both current and noncurrent (see Note 17). The Company may incur additional future expense if it is unable to sublease other locations included in the Facilities Initiative.

GENBAND Merger Restructuring Initiative

In connection with the merger in 2017 between Sonus Networks, Inc. and GENBAND (the "GENBAND Merger"), the Company implemented a restructuring plan in the fourth quarter of 2017 to eliminate certain redundant positions and facilities within the combined companies (the "GENBAND Merger Restructuring Initiative"). In connection with this initiative, the Company recorded $4.9 million in the three months ended March 31, 2019, virtually all of which was for severance and related costs for approximately 40 employees. The GENBAND Merger Restructuring Initiative is substantially complete, and the Company anticipates that it will record nominal future expense, if any, in connection with this initiative, with amounts accrued at March 31, 2020 to be paid by the end of 2020.

A summary of the GENBAND Merger Restructuring Initiative accrual activity for the three months ended March 31, 2020 is as follows (in thousands):



	Balance at January 1, 2020		Cash payments			Balance at March 31, 2020
Severance	$	409	$	(351	)	$	58

Balance Sheet Classification

The current portions of accrued restructuring are included as a component of Accrued expenses and the long-term portions of accrued restructuring are included as a component of Other long-term liabilities in the condensed consolidated balance sheets. The long-term portions of accrued restructuring totaled $0.9 million at both March 31, 2020 and December 31, 2019.

WARRANTY ACCRUALS

3 Months Ended

Mar. 31, 2020

Guarantees and Product Warranties [Abstract]

WARRANTY ACCRUALS

The changes in the Company's accrual balance in the three months ended March 31, 2020 were as follows (in thousands):



Balance at January 1, 2020	$	—
Assumed liability in connection with ECI Merger	15,706
Current period provisions	502
Settlements	(528		)
Balance at March 31, 2020	$	15,680

Of the amount recorded at March 31, 2020, $6.7 million was current and included as a component of Accrued expenses and other and $9.0 million was long-term and included as a component of Other long-term liabilities in the Company's condensed consolidated balance sheet. The Company did not have a warranty accrual during the three months ended March 31, 2019.

DEBT	3 Months Ended
DEBT	Mar. 31, 2020
Debt Disclosure [Abstract]
DEBT	DEBT Senior Secured Credit Facility On December 21, 2017, the Company entered into a Senior Secured Credit Facilities Credit Agreement (the “Credit Facility”), by and among the Company, as a guarantor, Sonus Networks, Inc., as the borrower (“Borrower”), Silicon Valley Bank ("SVB"), as administrative agent (in such capacity, the “Administrative Agent”), issuing lender, swingline lender and lead arranger and the lenders party thereto (each referred to individually as a “Lender”, and collectively, the “Lenders”), which refinanced the prior credit agreement with SVB that the Company had assumed in connection with the GENBAND Merger. The Credit Facility included $100 million of commitments, the full amount of which was available for revolving loans, a $15 million sublimit that was available for letters of credit and a $15 million sublimit that was available for swingline loans. On June 24, 2018, the Company amended the Credit Facility to, among other things, permit the August 2018 acquisition of Edgewater Networks, Inc. and related transactions. 2019 Credit Facility On April 29, 2019, the Company entered into a syndicated, amended and restated Credit Facility (the "2019 Credit Facility"). The 2019 Credit Facility provided for a $50 million term loan facility that was advanced in full on April 29, 2019 and a $100 million revolving line of credit. The 2019 Credit Facility also included procedures for additional financial institutions to become syndicate lenders, or for any existing lender to increase its commitment under either the term loan facility or the revolving loan facility, subject to an aggregate increase of $75 million for incremental commitments under the 2019 Credit Facility. The 2019 Credit Facility was scheduled to mature in April 2024. At December 31, 2019, the Company had an outstanding term loan debt balance of $48.8 million and an outstanding revolving line of credit balance of $8 million with a combined average interest rate of 3.30%, and $5.4 million of outstanding letters of credit at an interest rate of 1.50%. The indebtedness and other obligations under the 2019 Credit Facility were unconditionally guaranteed on a senior secured basis by the Company and each other material U.S. domestic subsidiary of the Company (collectively, the “Guarantors”). The 2019 Credit Facility was secured by first-priority liens on substantially all of the assets of the Borrower and the Guarantors, including the Company. The 2019 Credit Facility required periodic interest payments on any outstanding borrowings under the facility. The Borrower could prepay all revolving loans under the 2019 Credit Facility at any time without premium or penalty (other than customary LIBOR breakage costs), subject to certain notice requirements. Revolving loans under the 2019 Credit Facility bore interest at the Borrower’s option at either the Eurodollar (LIBOR) rate plus a margin ranging from 1.50% to 3.00% per year or the base rate (the highest of the Federal Funds rate plus 0.50%, or the prime rate announced from time to time in The Wall Street Journal) plus a margin ranging from 0.50% to 2.00% per year (such margins being referred to as the “Applicable Margin”). The Applicable Margin varied depending on the Company’s consolidated leverage ratio (as defined in the 2019 Credit Facility). The base rate and the LIBOR rate were each subject to a zero percent floor. The 2019 Credit Facility required compliance with certain financial covenants, including a minimum consolidated quick ratio, minimum consolidated fixed charge coverage ratio and maximum consolidated leverage ratio, all of which were defined in the 2019 Credit Facility and tested on a quarterly basis. The Company was in compliance with all covenants of the 2019 Credit Facility at December 31, 2019. In addition, the 2019 Credit Facility contained various covenants that, among other restrictions, limited the Company’s and its subsidiaries’ ability to enter into certain types of transactions, including, but not limited to: incurring or assuming indebtedness; granting or assuming liens; making acquisitions or engaging in mergers; making dividend and certain other restricted payments; making investments; selling or otherwise transferring assets; engaging in transactions with affiliates; entering into sale and leaseback transactions; entering into burdensome agreements; changing the nature of its business; modifying its organizational documents; and amending or making prepayments on certain junior debt. The 2019 Credit Facility contained events of default that are customary for a secured credit facility. If an event of default relating to bankruptcy or other insolvency events with respect to a borrower occurred, all obligations under the 2019 Credit Facility would immediately become due and payable. If any other event of default existed under the 2019 Credit Facility, the lenders could accelerate the maturity of the obligations outstanding under the 2019 Credit Facility and exercise other rights and remedies, including charging a default rate of interest equal to 2.00% per year above the rate that would otherwise be applicable. In addition, if any event of default existed under the New Credit Facility, the lenders could commence foreclosure or other actions against the collateral. If any default existed under the 2019 Credit Facility, or if the Borrower was unable to make any of the representations and warranties as stated in the 2019 Credit Facility at the applicable time, the Borrower would be unable to borrow funds or have letters of credit issued under the 2019 Credit Facility, which, depending on the circumstances prevailing at that time, could have had a material adverse effect on the Borrower’s liquidity and working capital. 2020 Credit Facility On March 3, 2020, the Company entered into a Senior Secured Credit Facilities Credit Agreement (the "2020 Credit Agreement"), by and among the Company, as a guarantor, Ribbon Communications Operating Company, Inc., as the borrower ("Borrower"), Citizens Bank, N.A., as administrative agent, a lender, issuing lender, swingline lender, joint lead arranger and bookrunner, Santander Bank, N.A., as a lender, joint lead arranger and bookrunner, and the other lenders party thereto (each, together with Citizens Bank, N.A. and Santander Bank, N.A., referred to individually as a "Lender", and collectively, the "Lenders"). The proceeds of the Credit Agreement were used, in part, to pay off in full all obligations of the Company under the 2019 Credit Facility. The 2020 Credit Agreement provides for $500 million of commitments from the lenders to the Borrower, comprised of a $400 million term loan (the "2020 Term Loan Facility") and a $100 million facility available for revolving loans (the "2020 Revolving Credit Facility" and together with the 2020 Term Loan Facility, the "2020 Credit Facility"). Under the 2020 Revolving Credit Facility, a $30 million sublimit is available for letters of credit and a $20 million sublimit is available for swingline loans. The 2020 Credit Facility is scheduled to mature in March 2025. Under the 2020 Credit Agreement, the Company is required to make quarterly principal payments aggregating $10 million over the next twelve months, $20 million per year for the following three years, and $30 million in the last year, with a $300 million final payment due on the maturity date. The 2020 Credit Agreement includes procedures for additional financial institutions to become lenders thereunder, or for any existing lender to fund one or more new tranches of term loans, or increase its commitment under the 2020 Term Loan Facility or the 2020 Revolving Credit Facility, subject, in each case, to an aggregate dollar limit equal to 100% of the Company's Consolidated Adjusted EBITDA (as defined in the 2020 Credit Agreement) as of the most recently ended quarter for which financial statements have been delivered to the lenders, plus additional amounts, so long as the Borrower's Consolidated Net Leverage Ratio (as defined in the 2020 Credit Agreement) does not exceed 2.75:1.00. The indebtedness and other obligations under the 2020 Credit Facility are unconditionally guaranteed on a senior secured basis by the Company, Edgewater Networks, Inc., a wholly-owned subsidiary of the Company, and Genband Inc., a wholly-owned subsidiary of the Company (together, the "Guarantors"). The 2020 Credit Facility is secured by first-priority liens on substantially all of the assets of the Borrower and the Guarantors, including substantially all of the assets of the Company. The 2020 Credit Agreement requires periodic interest payments until maturity. The Borrower may prepay all loans under the 2020 Credit Agreement at any time without premium or penalty (other than customary LIBOR breakage costs), subject to certain notice requirements. Loans incurred under the 2020 Credit Facility bear interest at the Borrower's option at either the LIBOR rate plus a margin ranging from 1.50% to 3.50% per year, or the base rate (the highest of the Federal Funds Effective Rate (as defined in the Credit Agreement) plus 0.5%, or the prime rate announced from time to time in The Wall Street Journal) plus a margin ranging from 0.50% to 2.50% per year (the "Applicable Margin"). The Applicable Margin varies depending on the Company's Consolidated Net Leverage Ratio (as defined in the 2020 Credit Agreement). The base rate and the LIBOR rate are each subject to a zero percent floor. The 2020 Credit Agreement requires compliance with certain financial covenants, including a minimum Consolidated Fixed Charge Coverage Ratio and a maximum Consolidated Net Leverage Ratio (each as defined in the 2020 Credit Agreement, and each tested on a quarterly basis). The Company was in compliance with all covenants of the 2020 Credit Agreement at March 31, 2020. In addition, the 2020 Credit Agreement contains various covenants that, among other restrictions, limit the Company’s and its subsidiaries’ ability to incur or assume indebtedness; grant or assume liens; make acquisitions or engage in mergers; sell, transfer, assign or convey assets; repurchase equity and make dividend and certain other restricted payments; make investments; engage in transactions with affiliates; enter into sale and leaseback transactions; enter into burdensome agreements; change the nature of its business; modify their organizational documents; and amend or make prepayments on certain junior debt. The 2020 Credit Agreement contains events of default that are customary for a secured credit facility. If an event of default relating to bankruptcy or other insolvency events with respect to the Company or any of its subsidiaries occurs, all obligations under the 2020 Credit Agreement will immediately become due and payable. If any other event of default exists under the 2020 Credit Agreement, the lenders may accelerate the maturity of the obligations outstanding under the Credit Agreement and exercise other rights and remedies, including charging a default rate of interest equal to 2.00% per year above the rate that would otherwise be applicable. In addition, if any event of default exists under the 2020 Credit Agreement, the lenders may commence foreclosure or other actions against the collateral. At March 31, 2020, the Company had an outstanding 2020 Term Loan Facility balance of $400 million at an average interest rate of 3.9%. The 2020 Revolving Credit Facility did not have an outstanding balance but had $5.6 million of letters of credit outstanding with an interest rate of 3.0%. Short-Term Loans The Company has three outstanding uncommitted and unsecured short-term loans aggregating $3.5 million which it uses for financing exports in China, two of which are with China Zheshang Bank and one of which is with Bank of Communications Hangzhou Branch. These short term loans were all entered into in March 2020 and expire at various dates in June and July 2020. At March 31, 2020, these short-term loans had a weighted average interest rate of 3.97%. Letters of Credit and Performance and Bid Bonds The Company uses letters of credit, performance and bid bonds in the course of its business. As of March 31, 2020, the Company had $33.3 million of letters of credit, bank guarantees, performance and bid bonds outstanding (collectively, "Guarantees"), comprised of the $5.6 million of letters of credit under the 2020 Credit Agreement described above, and $27.7 million of Guarantees under various uncommitted facilities. At March 31, 2020, the Company had cash collateral of $4.7 million supporting the Guarantees under its uncommitted facilities. This cash collateral is included in Restricted cash in the condensed consolidated balance sheet at March 31, 2020.

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES

3 Months Ended

Mar. 31, 2020

Derivative Instruments and Hedging Activities Disclosure [Abstract]

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES

The Company is exposed to financial market risk related to foreign currency fluctuations and changes in interest rates. These exposures are actively monitored by management. To manage the volatility related to the exposure to changes in interest rates, the Company has entered into a derivative financial instrument. Management's objective is to reduce, where it is deemed appropriate to do so, fluctuations in earnings and cash flows associated with changes in interest rates. Ribbon's policies and practices are to use derivative financial instruments only to the extent necessary to manage exposures. Ribbon does not hold or issue derivative financial instruments for trading or speculative purposes.

The Company records derivatives on the balance sheet at fair value. The accounting for changes in the fair value of derivatives depends on the intended use of the derivative, whether the Company has elected to designate a derivative in a hedging relationship and apply hedge accounting and whether the hedging relationship has satisfied the criteria necessary to apply hedge accounting. Derivatives designated and qualifying as a hedge of the exposure to changes in the fair value of an asset, liability, or firm commitment attributable to a specific risk, such as interest rate risk, are considered fair value hedges. Derivatives designated and qualifying as a hedge of the exposure to variability in expected future cash flows, or other types of forecasted transactions, are considered cash flow hedges. Derivatives may also be designated as hedges of the foreign currency exposure of a net investment in a foreign operation. Hedge accounting generally provides for the matching of the timing of gain or loss recognition on the hedging instrument with the recognition of the changes in the fair value of the hedged asset or liability that are attributable to the hedged risk in a fair value hedge, or the earnings effect of the hedged forecasted transactions in a cash flow hedge. The Company may enter into derivative contracts that are intended to economically hedge certain of its risk even though hedge accounting does not apply or the Company elects not to apply hedge accounting.

Cash Flow Hedge of Interest Rate Risk

The 2020 Credit Facility is comprised of the 2020 Term Loan Facility and the 2020 Revolving Credit Facility. The 2020 Term Loan Facility had an outstanding balance of $400 million at March 31, 2020. The 2020 Revolving Credit Facility was undrawn at March 31, 2020. The 2020 Credit Facility has variable interest rates based on LIBOR (see Note 9). As a result of exposure to interest rate movements, during March 2020, the Company entered into an interest rate swap arrangement, which effectively converted its $400 million term loan with its variable-rate interest based upon one-month LIBOR to an aggregate fixed rate of 0.904%, plus a leverage-based margin as defined in the 2020 Credit Facility. The notional amount of this swap as of March 31, 2020 was $400 million and the swap matures on March 3, 2025, the same date the 2020 Credit Facility matures.

The Company’s objectives in using interest rate derivatives are to add stability to interest expense and to manage its exposure to interest rate movements. To accomplish this objective, the Company is using an interest rate swap as part of its interest rate risk management strategy. Interest rate swaps designated as cash flow hedges involve the receipt of variable amounts from a counterparty in exchange for the Company making fixed-rate payments over the life of the agreements without exchange of the underlying notional amount.

The effective portion of changes in the fair value of derivatives designated and that qualify as cash flow hedges is recorded in accumulated other comprehensive income in the condensed consolidated balance sheet and is subsequently reclassified into earnings in the period that the hedged forecasted transactions affect earnings. During the three months ended March 31, 2020, such a derivative was used to hedge the variable cash flows associated with the 2020 Credit Facility. Any ineffective portion of the change in fair value of the derivative would be recognized directly in earnings. However, during the three months ended March 31, 2020, there was no hedge ineffectiveness recorded by the Company.

Amounts reported in accumulated other comprehensive income related to the Company's derivative will be reclassified to interest expense as interest is accrued on the Company’s variable-rate debt. Based upon projected forward rates, the Company estimates as of March 31, 2020 that $2.4 million may be reclassified as an increase to interest expense over the next twelve months.

The impact of the Company’s derivative financial instrument on its condensed consolidated statement of comprehensive loss for the three months ended March 31, 2020 was as follows (in thousands):



Loss recognized in other comprehensive loss on derivative (effective portion)	$	(9,717	)
Amount reclassified from accumulated other comprehensive loss to interest expense (effective portion)	$	190

The Company's derivative liability designed as a hedging instrument and the related fair values and locations in the condensed consolidated balance sheet at March 31, 2020 are as follows (in thousands):



	Balance sheet location
Interest rate derivative - liability derivative	Accrued expenses and other	$	(238	)
Interest rate derivative - liability derivative	Other long-term liabilities	$	(9,289	)

The Company has classified the interest rate derivative aggregating $9.5 million at March 31, 2020 as a Level 2 within the fair value hierarchy (see Note 1).

REVENUE RECOGNITION

3 Months Ended

Mar. 31, 2020

Revenue from Contract with Customer [Abstract]

REVENUE RECOGNITION

The Company accounts for revenue in accordance with ASC 606, Revenue from Contracts with Customers ("ASC 606"), which it adopted on January 1, 2018 using the modified retrospective method.

The Company derives revenues from two primary sources: products and services. Product revenue includes the Company's hardware and software that function together to deliver the products' essential functionality. Software and hardware are also sold on a standalone basis. Services include customer support (software updates, upgrades and technical support), consulting, design services, installation services and training. Generally, contracts with customers contain multiple performance obligations, consisting of products and services. For these contracts, the Company accounts for individual performance obligations separately if they are considered distinct.

When an arrangement contains more than one performance obligation, the Company will generally allocate the transaction price to each performance obligation on a relative standalone selling price basis. The best evidence of a standalone selling price is the observable price of a good or service when the entity sells that good or service separately in similar circumstances and to similar customers. If the good or service is not sold separately, an entity must estimate the standalone selling price by using an approach that maximizes the use of observable inputs. Acceptable estimation methods include but are not limited to: (1) adjusted market assessment; (2) expected cost plus a margin; and (3) a residual approach (when the standalone selling price is not directly observable and is either highly variable or uncertain).

The Company's software licenses typically provide a perpetual right to use the Company's software. The Company also sells term-based software licenses that expire and Software-as-a-Service ("SaaS")-based software which are referred to as subscription arrangements. The Company does not customize its software nor are installation services required, as the customer has a right to utilize internal resources or a third-party service company. The software and hardware are delivered before related services are provided and are functional without professional services or customer support. The Company has concluded that its software licenses are functional intellectual property that are distinct, as the user can benefit from the software on its own. The product revenue is typically recognized upon transfer of control or when the software is made available for download, as this is the point that the user of the software can direct the use of, and obtain substantially all of the remaining benefits from, the functional intellectual property. The Company does not recognize software revenue related to the renewal of subscription software licenses earlier than the beginning of the subscription period. Hardware product is generally sold with software to provide the customer solution.

Services revenue includes revenue from customer support and other professional services. The Company offers warranties on its products. Certain of the Company's warranties are considered to be assurance-type in nature and do not cover anything beyond ensuring that the product is functioning as intended. Based on the guidance in ASC 606, assurance-type warranties do not represent separate performance obligations. The Company also sells separately-priced maintenance service contracts, which qualify as service-type warranties and represent separate performance obligations. The Company does not allow and has no history of accepting product returns.

Customer support includes software updates on a when-and-if-available basis, telephone support, integrated web-based support and bug fixes or patches. The Company sells its customer support contracts at a percentage of list or net product price related to the support. Customer support revenue is recognized ratably over the term of the customer support agreement, which is typically one year.

The Company's professional services include consulting, technical support, resident engineer services, design services and installation services. Because control transfers over time, revenue is recognized based on progress toward completion of the performance obligation. The method to measure progress toward completion requires judgment and is based on the nature of the products or services to be provided. The Company generally uses the input method to measure progress for its contracts because it believes such method best depicts the transfer of assets to the customer, which occurs as the Company incurs costs for the contracts. Under the cost-to-cost measure of progress, the progress toward completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation. When the measure of progress is based upon expended labor, progress toward completion is measured as the ratio of labor time expended to date versus the total estimated labor time required to complete the performance obligation. Revenue is recorded proportionally as costs are incurred or labor is expended. Costs to fulfill these obligations include internal labor as well as subcontractor costs.

Customer training includes courses offered by the Company. The related revenue is typically recognized as the training services are performed.

The Company's typical performance obligations include the following:



Performance Obligation	When Performance Obligation is Typically Satisfied	When Payment is Typically Due
Software and Product Revenue
Software licenses (perpetual or term)	Upon transfer of control; typically, when made available for download (point in time)	Generally, within 30 days of invoicing except for term licenses, which may be paid for over time

Software licenses (subscription)	Upon activation of hosted site (over time)	Generally, within 30 days of invoicing

Appliances	When control of the appliance passes to the customer; typically, upon delivery (point in time)	Generally, within 30 days of invoicing

Software upgrades	Upon transfer of control; typically, when made available for download (point in time)	Generally, within 30 days of invoicing

Customer Support Revenue
Customer support	Ratably over the course of the support contract (over time)	Generally, within 30 days of invoicing

Professional Services
Other professional services (excluding training services)	As work is performed (over time)	Generally, within 30 days of invoicing (upon completion of services)

Training	When the class is taught (point in time)	Generally, within 30 days of services being performed

Significant Judgments

The Company's contracts with customers often include promises to transfer multiple products and services to the customer. Determining whether products and services are considered distinct performance obligations that should be accounted for separately versus together may require significant judgment.

Judgment is required to determine the standalone selling price ("SSP") for each distinct performance obligation. The Company typically has more than one SSP for individual products and services due to the stratification of those products and services by customers and circumstances. In these instances, the Company may use information such as the size of the customer and geographic region in determining the SSP.

Deferred Revenue

Deferred revenue is a contract liability representing amounts collected from or invoiced to customers in excess of revenue recognized. This results primarily from the billing of annual customer support agreements where the revenue is recognized over the term of the agreement. The value of deferred revenue will increase or decrease based on the timing of recognition of revenue.

Disaggregation of Revenue

The Company disaggregates its revenue from contracts with customers based on the nature of the products and services and the geographic regions in which each customer is domiciled. The Company's revenue for the three months ended March 31, 2020 and 2019 was disaggregated as follows:



Three months ended March 31, 2020	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	36,365	$	31,466	$	10,566	$	78,397
Europe, Middle East and Africa	20,365		14,810		4,015		39,190
Japan	4,952		2,874		2,614		10,440
Asia Pacific	9,991		4,637		2,264		16,892
Other	4,226		7,281		1,556		13,063
	$	75,899	$	61,068	$	21,015	$	157,982



Three months ended March 31, 2019	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	28,446	$	32,787	$	7,343	$	68,576
Europe, Middle East and Africa	6,458		10,723		2,849		20,030
Japan	3,961		2,913		1,562		8,436
Asia Pacific	4,675		3,663		869		9,207
Other	3,940		6,903		1,836		12,679
	$	47,480	$	56,989	$	14,459	$	118,928

The Company's product revenue from indirect sales through its channel partner program and from its direct sales program for the three months ended March 31, 2020 and 2019 was as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019
Indirect sales through channel partner program	$	28,604	$	19,174
Direct sales	47,295		28,306
	$	75,899	$	47,480

The Company's product revenue from sales to enterprise customers and from sales to service provider customers for the three months ended March 31, 2020 and 2019 was as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019
Sales to enterprise customers	$	27,281	$	14,755
Sales to service provider customers	48,618		32,725
	$	75,899	$	47,480

Revenue Contract Balances

The timing of revenue recognition, billings and cash collections results in billed accounts receivable; unbilled receivables, which are contract assets; and customer advances and deposits, which are contract liabilities, in the Company's condensed consolidated balance sheets. Amounts are billed as work progresses in accordance with agreed-upon contractual terms, either at periodic intervals or upon achievement of contractual milestones. Completion of services and billing may occur subsequent to revenue recognition, resulting in contract assets. The Company may receive advances or deposits from its customers before revenue is recognized, resulting in contract liabilities that are classified as deferred revenue. These assets and liabilities are reported in the Company's condensed consolidated balance sheets on a contract-by-contract basis as of the end of each reporting period. Changes in the contract asset and liability balances during the three months ended March 31, 2020 were not materially impacted by any factors other than billing and revenue recognition. Nearly all of the Company's deferred revenue balance is related to services revenue, primarily customer support contracts. Unbilled receivables stem primarily from engagements where services have been performed; however, billing cannot occur until services are completed.

In some arrangements, the Company allows customers to pay for term-based software licenses and products over the term of the software license. The Company also sells SaaS-based software under subscription arrangements, with payment terms over the term of the SaaS agreement. Amounts recognized as revenue in excess of amounts billed are recorded as unbilled receivables. Unbilled receivables that are anticipated to be invoiced in the next twelve months are included in Accounts receivable on the Company's condensed consolidated balance sheets. The changes in the Company's accounts receivable, unbilled receivables and deferred revenue balances for the three months ended March 31, 2020 were as follows (in thousands):



	Accounts receivable		Unbilled accounts receivable		Deferred revenue (current)		Deferred revenue (long-term)
Balance at January 1, 2020	$	168,502	$	24,204	$	100,406	$	20,482
Increase (decrease), net	1,286		11,801		13,293		5,429
Balance at March 31, 2020	$	169,788	$	36,005	$	113,699	$	25,911

The Company recognized approximately $41 million of revenue in the three months ended March 31, 2020 that was recorded as deferred revenue at December 31, 2019 and approximately $33 million of revenue in the three months ended March 31, 2019 that was recorded as deferred revenue at December 31, 2018. Of the Company's deferred revenue reported as long-term in its condensed consolidated balance sheet at March 31, 2020, the Company expects that approximately $12 million will be recognized as revenue in 2021, approximately $8 million will be recognized as revenue in 2022 and approximately $6 million will be recognized as revenue in 2023 and beyond.

All freight-related customer invoicing is recorded as revenue, while the shipping and handling costs that occur after control of the promised goods or services transfer to the customer are reported as fulfillment costs, a component of Cost of revenue - product in the Company's condensed consolidated statements of operations.

Deferred Commissions Cost

Sales commissions earned by the Company's employees are considered incremental and recoverable costs of obtaining a contract with a customer. Expense related to commission payments has been deferred on our condensed consolidated balance sheet and is being amortized over the expected life of the customer contract, which averages five years. At both March 31, 2020 and December 31, 2019, the Company had $3.6 million of deferred sales commissions capitalized.

COMMON STOCK REPURCHASES	3 Months Ended
COMMON STOCK REPURCHASES	Mar. 31, 2020
Equity [Abstract]
COMMON STOCK REPURCHASES	COMMON STOCK REPURCHASES In the second quarter of 2019, the Board approved a stock repurchase program (the "Repurchase Program") pursuant to which the Company may repurchase up to $75 million of the Company's common stock prior to April 18, 2021. Repurchases under the Repurchase Program may be made in the open market, in privately negotiated transactions or otherwise, with the amount and timing of repurchases depending on market conditions and corporate discretion. The Repurchase Program does not obligate the Company to acquire any particular amount of common stock and may be extended, modified, suspended or discontinued at any time at the Board's discretion. The stock repurchases are being funded using the Company's working capital. The Company did not repurchase any stock during the three months ended March 31, 2020. At March 31, 2020, the Company had $70.5 million remaining under the Repurchase Program for future repurchases.

STOCK-BASED COMPENSATION PLANS

3 Months Ended

Mar. 31, 2020

Share-based Payment Arrangement [Abstract]

STOCK-BASED COMPENSATION PLANS

2019 Stock Incentive Plan

The Company's 2019 Incentive Award Plan (the "2019 Plan") provides for the award of options to purchase the Company's common stock ("stock options"), stock appreciation rights ("SARs"), restricted stock awards ("RSAs"), performance-based stock awards ("PSAs"), restricted stock units ("RSUs"), performance-based stock units ("PSUs") and other stock- or cash-based awards. Awards can be granted under the 2019 Plan to the Company's employees, officers and non-employee directors, as well as consultants and advisors of the Company and its subsidiaries.

2007 Plan

The Company's 2007 Plan provided for the award of stock options, SARs, RSAs, RSU, PSAs, PSUs and other stock-based awards to employees, officers, non-employee directors, consultants and advisors of the Company and its subsidiaries. On and following June 5, 2019, with the exception of shares underlying awards outstanding as of that date, no additional shares may be granted under the 2007 Plan.

Assumed Stock Plans

In connection with the Edgewater Acquisition, the Company assumed Edgewater's Amended and Restated 2002 Stock Option Plan (the "Edgewater Plan") to the extent of the shares underlying the options outstanding under the Edgewater Plan as of the Edgewater Acquisition Date (the "Edgewater Options"). The Edgewater Options were converted to Ribbon stock options (the "Ribbon Replacement Options") which are vesting under the same schedules as the respective Edgewater Options.

In connection with the Company's acquisitions of Performance Technologies Inc. ("PT") in 2014, and Network Equipment Technologies, Inc. ("NET") in 2012, the Company assumed their stock plans (collectively, the "Assumed Plans"). Any outstanding awards under the Assumed Plans that in the future expire, terminate, are cancelled or surrendered, or are repurchased by the Company will be returned to the 2019 Plan. Accordingly, at March 31, 2020, no additional shares may be granted under the Assumed Plans.

Executive Equity Arrangements

Inducement Awards

In connection with his appointment as President and Chief Executive Office of Ribbon, and as an inducement for Bruce McClelland's ("Mr. McClelland") commencement of employment, the Company awarded Mr. McClelland sign-on equity grants, comprised of an RSU grant and a PSU grant with both market and service conditions (the "Inducement PSUs") on March 16, 2020. Subject to Mr. McClelland's continued employment, 462,963 RSUs are eligible to vest on the earlier of March 16, 2021 or the date of the consummation of a change in control of the Company and, upon vesting, will be settled in shares of Ribbon's common stock. The RSUs had a fair market value of $1.0 million on the date of grant. Subject to Mr. McClelland's continued employment, the PSUs are eligible to vest and be settled in up to 4,750,000 shares of Ribbon common stock upon the achievement of specified share price thresholds on or prior to September 1, 2024. These grants are reported in the applicable tables below.

Other Performance-Based Stock Grants

In addition to granting RSAs and RSUs to its executives and certain of its employees, the Company also grants PSUs to certain of its executives, including the Inducement PSUs granted to Mr. McClelland as described above.

2019 PSU Grants. In March and April 2019, the Company granted certain of its executives an aggregate of 872,073 PSUs, of which 523,244 PSUs had both performance and service conditions (the "Performance PSUs") and 348,829 PSUs had both market and service conditions (the "Market PSUs").

Each executive's Performance PSU grant is comprised of three consecutive fiscal year performance periods from 2019 through 2021 (each, a "Fiscal Year Performance Period"), with one-third of the Performance PSUs attributable to each Fiscal Year Performance Period. The number of shares that will vest for each Fiscal Year Performance Period will be based on the achievement of certain metrics related to the Company's financial performance for the applicable year on a standalone basis (each, a "Fiscal Year Performance Condition"). In the third quarter of 2019, the Company adjusted the 2019 Performance PSU goals to reflect the changes to the Company's calculation of certain metrics. There was no incremental expense in connection with this modification. In March 2020, the Compensation Committee determined that the performance metrics for the 2019 Performance PSUs had been achieved at the 30.493% level. The Company's achievement of the 2019 Fiscal Year Performance Conditions (and the number of shares of Company common stock to vest as a result thereof) was measured on a linear sliding scale in relation to specific threshold, target and stretch performance conditions. The Company is recording stock-based compensation expense for the Performance PSUs based on its assessment of the probability that each performance condition will be achieved and the level, if any, of such achievement. As of March 31, 2020, the Company determined that the grant date criteria for the 2020 and 2021 Fiscal Year Performance Periods had not been met, as the 2020 and 2021 Fiscal Year Performance Conditions had not been established by the Company. Accordingly, the stock-based compensation expense recorded in the three months ended March 31, 2020 in connection with the Performance PSUs is related only to those number of shares representing the final achievement level for the PSUs with 2019 Fiscal Year Performance Conditions. The Compensation Committee will determine the number of shares earned, if any, after the Company's financial results for each Fiscal Year Performance Period are finalized. Upon the determination by the Compensation Committee of the number of shares that will be received upon vesting of the Performance PSUs, such number of shares will become fixed and the unamortized expense will be recorded through the remainder of the service period that ends March 15, 2022, at which time the total Performance PSUs earned, if any, will vest, pending each executive's continued employment with the Company through that date. The number of shares of common stock to be achieved upon vesting of the Performance PSUs will in no event exceed 200% of the Performance PSUs. Shares subject to the Performance PSUs that fail to be earned will be forfeited.

The Market PSUs have one three-year performance period which will end on December 31, 2021 (the "Market Performance Period"). The number of shares subject to the Market PSUs that will vest, if any, on March 15, 2022, will be dependent upon the Company's total shareholder return ("TSR") compared with the TSR of the companies included in the Nasdaq Telecommunications Index for the same Market Performance Period, measured by the Compensation Committee after the Market Performance Period ends. The shares determined to be earned will vest on March 15, 2022, pending each executive's continued employment with the Company through that date. The number of shares of common stock to be achieved upon vesting of the Market PSUs will in no event exceed 200% of the Market PSUs. Shares subject to the Market PSUs that fail to be earned will be forfeited.

2018 PSU Grant. In May 2018, the Company granted Franklin Hobbs, the Company's former President and Chief Executive Officer ("Mr. Hobbs"), 195,000 PSUs with both performance and service conditions (the "2018 PSUs"). Of the 195,000 2018 PSUs, one-half of such PSUs were eligible to vest based on the achievement of two separate metrics related to the Company's 2018 financial performance (the "2018 Performance Conditions"). The Company's achievement of the 2018 Performance Conditions (and the number of shares of Company common stock to be received upon vesting as a result thereof) were measured on a linear sliding scale in relation to specific threshold, target and stretch performance conditions. The number of shares of common stock to be received upon vesting of the 2018 PSUs would in no event exceed 150% of the 2018 PSUs. The Compensation Committee determined that the performance metrics for all of the 2018 PSUs had been achieved at the 150% level, for a total of 292,500 shares eligible to be issued. In connection with Mr. Hobbs' separation from the Company effective December 31, 2019, the vesting schedule for the 2018 Shares earned was accelerated and the shares were released on January 30, 2020.

Accounting for PSUs with Market Conditions. PSUs that include a market condition require the use of a Monte Carlo simulation approach to model future stock price movements based upon the risk-free rate of return, the date of return, the volatility of each entity and the pair-wise covariance between each entity. These results are then used to calculate the grant date fair values of the respective PSUs. The Company is required to record expense for the PSUs with market conditions through their respective final vesting dates, regardless of the number of shares that are ultimately earned. As of March 31, 2020, the calculation of the grant date fair value of the Inducement PSUs had not been completed. The Company used a grant date fair value of $2.16, the closing stock price on the date of grant, to calculate expense attributable to the three months ended March 31, 2020 for the Inducement PSUs. The Company is also using this stock price for PSU activity reported in the PSU table below. Upon completion of the Monte Carlo analysis and finalization of the grant date fair value of the Inducement PSUs, which it expects to complete in the second quarter of 2020, the Company will record a cumulative adjustment to expense and adjust their grant date fair value for subsequent reporting. The Company does not expect the cumulative adjustment to expense will have a material impact on its consolidated financial statements.

Stock Options

The activity related to the Company's outstanding stock options for the three months ended March 31, 2020 was as follows:



	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2020	297,124		$	11.55
Granted	—		$	—
Exercised	(3,014	)	$	1.74
Forfeited	(1,470	)	$	1.80
Expired	(4,920	)	$	18.10
Outstanding at March 31, 2020	287,720		$	11.59	4.33	$	109
Vested or expected to vest at March 31, 2020	285,559		$	11.66	4.31	$	108
Exercisable at March 31, 2020	260,307		$	12.58	4.03	$	85

Additional information regarding the Company's stock options for the three months ended March 31, 2020 was as follows (in thousands):



Total intrinsic value of stock options exercised	$	5
Cash received from the exercise of stock options	$	5

Restricted Stock Awards and Units

The activity related to the Company's RSAs for the three months ended March 31, 2020 was as follows:



	Shares		Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2020	487,976		$	6.87
Granted	—		$	—
Vested	(89,920	)	$	7.04
Forfeited	(4,499	)	$	7.04
Unvested balance at March 31, 2020	393,557		$	6.83

The activity related to the Company's RSUs for the three months ended March 31, 2020 was as follows:



	Shares		Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2020	2,790,060		$	5.11
Granted	4,123,151		$	2.22
Vested	(927,062	)	$	4.81
Forfeited	(237,818	)	$	4.69
Unvested balance at March 31, 2020	5,748,331		$	3.10

The total grant date fair value of shares of restricted stock granted under RSAs and RSUs that vested during the three months ended March 31, 2020 was $5.1 million.

Performance-Based Stock Units

The activity related to the Company's PSUs for the three months ended March 31, 2020 was as follows:



	Shares		Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2020	1,067,073		$	5.94
Granted	4,847,500		$	2.23
Vested	(315,866	)	$	5.53
Forfeited	(359,777	)	$	5.51
Unvested balance at March 31, 2020	5,238,930		$	2.52

The total grant date fair value of shares of restricted stock granted under PSUs that vested during the three months ended March 31, 2020 was $1.7 million.

Employee Stock Purchase Plan

The Company's Amended and Restated 2000 Employee Stock Purchase Plan ("ESPP") is designed to provide eligible employees of the Company and its participating subsidiaries an opportunity to purchase common stock of the Company through accumulated payroll deductions. The ESPP provides for six-month offering periods with the purchase price of the stock equal to 85% of the lesser of the closing market price on the first or last day of the offering period. The maximum number of shares of common stock an employee may purchase during each offering period is 500, subject to certain adjustments pursuant to the ESPP. The last purchase under the ESPP purchase period ended on November 30, 2019.

Stock-Based Compensation

The condensed consolidated statements of operations include stock-based compensation for the three months ended March 31, 2020 and 2019 as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019
Product cost of revenue	$	27	$	14
Service cost of revenue	130		92
Research and development	558		507
Sales and marketing	752		984
General and administrative	1,509		2,542
	$	2,976	$	4,139

There was no income tax benefit for employee stock-based compensation expense for the three months ended March 31, 2020 or 2019 due to the valuation allowance recorded.

At March 31, 2020, there was $26.3 million, net of expected forfeitures, of unrecognized stock-based compensation expense related to unvested stock options, stock awards and stock units. This expense is expected to be recognized over a weighted average period of approximately three years.

MAJOR CUSTOMERS

3 Months Ended

Mar. 31, 2020

Risks and Uncertainties [Abstract]

MAJOR CUSTOMERS

The following customers contributed 10% or more of the Company's revenue in the three months ended March 31, 2020 and 2019:



	Three months ended
	March 31, 2020	March 31, 2019
Verizon Communications Inc.	13%	15%
AT&T Inc.	10%	10%

At March 31, 2020, there were no customers that accounted for 10% or more of the Company's accounts receivable balance. At December 31, 2019, one customer accounted for 10% or more of the Company's accounts receivable balance, representing approximately 22% of total accounts receivable. The Company performs ongoing credit evaluations of its customers and generally does not require collateral on accounts receivable, although in some instances the Company may require letters of credit to support customer outstanding accounts receivable balances. The Company maintains an allowance for doubtful accounts and such losses have been within management's expectations.

RELATED PARTY TRANSACTIONS	3 Months Ended
RELATED PARTY TRANSACTIONS	Mar. 31, 2020
Related Party Transactions [Abstract]
RELATED PARTY TRANSACTIONS	RELATED PARTY TRANSACTIONS As a portion of the consideration for the GENBAND Merger, on October 27, 2017, the Company issued a Promissory Note for $22.5 million to certain of GENBAND's equity holders who, following the GENBAND Merger, owned greater than five percent of the Company's outstanding shares. As described in Note 9, the Promissory Note did not amortize and the principal thereon was payable in full on the third anniversary of its execution. Interest on the Promissory Note was payable quarterly in arrears and accrued at a rate of 7.5% per year for the first six months after issuance, and thereafter at a rate of 10% per year. The failure to make any payment under the Promissory Note when due and, with respect to payment of any interest, the continuation of such failure for a period of thirty days thereafter, constituted an event of default under the Promissory Note. If an event of default occurred under the Promissory Note, the payees could declare the entire balance of the Promissory Note due and payable (including principal and accrued and unpaid interest) within five business days of the payees' notification to the Company of such acceleration. On April 29, 2019, the Company repaid in full all outstanding amounts under the Promissory Note, aggregating $24.7 million. The Company did not incur any early termination penalties in connection with this repayment.

INCOME TAXES	3 Months Ended
INCOME TAXES	Mar. 31, 2020
Income Tax Disclosure [Abstract]
INCOME TAXES	INCOME TAXES The Company's income tax provisions for the three months ended March 31, 2020 and 2019 reflect the Company's estimates of the effective rates expected to be applicable for the respective full years, adjusted for any discrete events, which are recorded in the period that they occur. These estimates are reevaluated each quarter based on the Company's estimated tax expense for the full year. The estimated effective tax rate includes the impact of valuation allowances in various jurisdictions. The Company continues to evaluate the impact of various COVID-19 relief packages offered by various countries, including the Coronavirus Aid, Relief, and Economic Security ("CARES") Act, which was enacted into law on March 27, 2020. At this time, the Company does not anticipate any material tax impacts.

LEASES

3 Months Ended

Mar. 31, 2020

Leases [Abstract]

LEASES

The Company has operating and finance leases for corporate offices, research and development facilities, and certain equipment. Operating leases are reported separately in the Company's condensed consolidated balance sheets. Assets acquired under finance leases are included in Property and equipment, net, in the condensed consolidated balance sheets.

The Company determines if an arrangement is a lease at inception. A contract is determined to contain a lease component if the arrangement provides the Company with a right to control the use of an identified asset. Lease agreements may include lease and non-lease components. In such instances for all classes of underlying assets, the Company does not separate lease and non-lease components but rather, accounts for the entire arrangement under leasing guidance. Leases with an initial term of 12 months or less are not recorded on the balance sheet and lease expense for these leases is recognized on a straight-line basis over the lease term.

Right-of-use assets and lease liabilities are initially measured based on the present value of the future minimum fixed lease payments (i.e., fixed payments in the lease contract) over the lease term at the commencement date. As the Company's existing leases do not have a readily determinable implicit rate, the Company uses its incremental borrowing rate based on the information available at the commencement date in determining the present value of future minimum fixed lease payments. The Company calculates its incremental borrowing rate to reflect the interest rate that it would have to pay to borrow on a collateralized basis an amount equal to the lease payments in a similar economic environment over a similar term and considers its historical borrowing activities and market data from entities with comparable credit ratings in this determination. The measurement of the right-of-use asset also includes any lease payments made prior to the commencement date (excluding any lease incentives) and initial direct costs incurred. The Company assessed its right-of-use assets for impairment as of March 31, 2020 and December 31, 2019 and determined no impairment has occurred.

Lease terms may include options to extend or terminate the lease and the Company incorporates such options in the lease term when it has the unilateral right to make such an election and it is reasonably certain that the Company will exercise that option. In making this determination, the Company considers its prior renewal and termination history and planned usage of the assets under lease, incorporating expected market conditions.

For operating leases, lease expense for minimum fixed lease payments is recognized on a straight-line basis over the lease term. The expense for finance leases includes both interest and amortization expense components, with the interest component calculated based on the effective interest method and the amortization component calculated based on straight-line amortization of the right-of-use asset over the lease term. Lease contracts may contain variable lease costs, such as common area maintenance, utilities and tax reimbursements that vary over the term of the contract. Variable lease costs are not included in minimum fixed lease payments and as a result, are excluded from the measurement of the right-of-use assets and lease liabilities. The Company expenses all variable lease costs as incurred.

In connection with the 2019 Restructuring Initiative, certain lease assets related to facilities will be partially or fully vacated as the Company consolidates its facilities. The Company has no plans to enter into sublease agreements for certain facilities. The Company ceased use of these facilities in the first quarter of 2020 and the third quarter of 2019. Accordingly, the Company accelerated the amortization of the associated lease assets through the planned cease-use date of each facility, resulting in additional amortization expense of $0.1 million in the three months ended March 31, 2020. The Company previously recorded $3.7 million of additional amortization expense in the year ended December 31, 2019. The Company did not record additional amortization expense in the three months ended March 31, 2019. The Company recorded nominal expense in the three months ended March 31, 2020 for estimated future variable lease costs. The Company did not record expense for future variable lease costs in the three months ended March 31, 2019 but recorded $0.9 million in the aggregate in the year ended December 31, 2019. All of these amounts were recorded as Restructuring and related expense in the Company's consolidated statements of operations. At both March 31, 2020 and December 31, 2019, the Company had accruals of $0.9 million for all future anticipated variable lease costs related to these facilities. The Company may incur additional future expense if it is unable to sublease other locations included in the Facilities Initiative.

The Company leases its corporate offices and other facilities under operating leases, which expire at various times through 2029. The Company's corporate headquarters is located in a leased facility in Westford, Massachusetts under a lease that expires in August 2028. The Company's finance leases primarily consist of equipment.

At March 31, 2020, the Company had 107,800 square feet of building space in North Dallas, Texas under construction as part of the Facilities Initiative. The Company's leased Plano, Texas facility will be vacated upon completion of the construction of the North Dallas, Texas site. At that time, employees will relocate to the new site as part of the Facilities Initiative. The construction of the new North Dallas, Texas site is expected to be completed in 2020.

The Company's right-of-use lease assets and lease liabilities at March 31, 2020 and December 31, 2019 were as follows (in thousands):



	Classification	March 31, 2020		December 31, 2019
Assets
Operating lease assets	Operating lease right-of-use assets	$	66,295	$	36,654
Finance lease assets*	Property and equipment, net	2,093		2,420
Total leased assets		$	68,388	$	39,074

Liabilities
Current
Operating	Operating lease liabilities	$	18,201	$	7,719
Finance	Accrued expenses and other	1,376		1,005
Noncurrent
Operating	Operating lease liabilities, net of current	55,857		37,202
Finance	Other long-term liabilities	1,436		2,144
Total lease liabilities		$	76,870	$	48,070

* Finance lease assets were recorded net of accumulated depreciation of $2.3 million and $2.0 million at March 31, 2020 and December 31, 2019, respectively.

The components of lease expense for the three months ended March 31, 2020 and 2019 were as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019

Operating lease cost*	$	3,344	$	2,441
Finance lease cost
Amortization of leased assets	319		244
Interest on lease liabilities	55		64
Short-term lease cost	5,523		4,671
Variable lease costs (costs excluded from minimum fixed lease payments)	637		601
Net lease cost	$	9,878	$	8,021

* Operating lease cost for the three months ended March 31, 2020 includes $0.1 million of accelerated amortization for certain assets partially or fully vacated in 2020 with no intent or ability to sublease.

Other information related to the Company's leases as of and for the three months ended March 31, 2020 and 2019 was as follows (in thousands, except lease terms and percentages):



	Three months ended
	March 31, 2020		March 31, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows for operating leases	$	3,113	$	2,355
Operating cash flows for finance leases	$	55	$	64
Financing cash flows for finance leases	$	338	$	230



	March 31, 2020		December 31, 2019
Weighted average remaining lease term (years)
Operating leases	5.36		6.73
Finance leases	2.19		2.35
Weighted average discount rate
Operating leases	5.58	%	6.50	%
Finance leases	7.49	%	7.54	%

Future minimum fixed lease payments under noncancelable leases at March 31, 2020 and December 31, 2019 were as follows (in thousands):



	March 31, 2020
	Operating			Finance
	leases			leases
Remainder of 2020	$	16,251		$	1,214
2021	19,067			1,179
2022	15,345			587
2023	12,889			36
2024	6,692			—
2025 and beyond	16,127			—
Total lease payments	86,371			3,016
Less: interest	(12,313		)	(204		)
Present value of lease liabilities	$	74,058		$	2,812



	December 31, 2019
	Operating			Finance
	leases			leases
2020	$	10,290		$	1,644
2021	9,468			1,159
2022	7,665			581
2023	7,067			—
2024	5,303			—
2025 and beyond	15,738			—
Total lease payments	55,531			3,384
Less: interest	(10,610		)	(235		)
Present value of lease liabilities	$	44,921		$	3,149

LEASES

The Company's right-of-use lease assets and lease liabilities at March 31, 2020 and December 31, 2019 were as follows (in thousands):



	Classification	March 31, 2020		December 31, 2019
Assets
Operating lease assets	Operating lease right-of-use assets	$	66,295	$	36,654
Finance lease assets*	Property and equipment, net	2,093		2,420
Total leased assets		$	68,388	$	39,074

Liabilities
Current
Operating	Operating lease liabilities	$	18,201	$	7,719
Finance	Accrued expenses and other	1,376		1,005
Noncurrent
Operating	Operating lease liabilities, net of current	55,857		37,202
Finance	Other long-term liabilities	1,436		2,144
Total lease liabilities		$	76,870	$	48,070

* Finance lease assets were recorded net of accumulated depreciation of $2.3 million and $2.0 million at March 31, 2020 and December 31, 2019, respectively.

The components of lease expense for the three months ended March 31, 2020 and 2019 were as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019

Operating lease cost*	$	3,344	$	2,441
Finance lease cost
Amortization of leased assets	319		244
Interest on lease liabilities	55		64
Short-term lease cost	5,523		4,671
Variable lease costs (costs excluded from minimum fixed lease payments)	637		601
Net lease cost	$	9,878	$	8,021

Other information related to the Company's leases as of and for the three months ended March 31, 2020 and 2019 was as follows (in thousands, except lease terms and percentages):



	Three months ended
	March 31, 2020		March 31, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows for operating leases	$	3,113	$	2,355
Operating cash flows for finance leases	$	55	$	64
Financing cash flows for finance leases	$	338	$	230



	March 31, 2020		December 31, 2019
Weighted average remaining lease term (years)
Operating leases	5.36		6.73
Finance leases	2.19		2.35
Weighted average discount rate
Operating leases	5.58	%	6.50	%
Finance leases	7.49	%	7.54	%

Future minimum fixed lease payments under noncancelable leases at March 31, 2020 and December 31, 2019 were as follows (in thousands):



	March 31, 2020
	Operating			Finance
	leases			leases
Remainder of 2020	$	16,251		$	1,214
2021	19,067			1,179
2022	15,345			587
2023	12,889			36
2024	6,692			—
2025 and beyond	16,127			—
Total lease payments	86,371			3,016
Less: interest	(12,313		)	(204		)
Present value of lease liabilities	$	74,058		$	2,812



	December 31, 2019
	Operating			Finance
	leases			leases
2020	$	10,290		$	1,644
2021	9,468			1,159
2022	7,665			581
2023	7,067			—
2024	5,303			—
2025 and beyond	15,738			—
Total lease payments	55,531			3,384
Less: interest	(10,610		)	(235		)
Present value of lease liabilities	$	44,921		$	3,149

COMMITMENTS AND CONTINGENCIES	3 Months Ended
COMMITMENTS AND CONTINGENCIES	Mar. 31, 2020
Commitments and Contingencies Disclosure [Abstract]
COMMITMENTS AND CONTINGENCIES	COMMITMENTS AND CONTINGENCIES Litigation Settlement As previously disclosed, the Company was involved in six lawsuits (together, the "Lawsuits") with Metaswitch Networks Ltd., Metaswitch Networks Corp. and Metaswitch Inc. (collectively, "Metaswitch"). In five of the Lawsuits, the Company was the plaintiff and, in three of those five lawsuits, the Company was also a counterclaim defendant. In the sixth case, the Company was the defendant. On April 22, 2019, the Company and Metaswitch agreed to a binding mediator's proposal that resolved the six Lawsuits between the Company and Metaswitch (the "Lawsuits"). The Company and Metaswitch signed a Settlement and Cross-License Agreement on May 29, 2019 (the "Royalty Agreement"). Pursuant to the terms of the Royalty Agreement, Metaswitch has agreed to pay the Company an aggregate amount of $63.0 million, which includes cash payments of $37.5 million during the second quarter of 2019 and $25.5 million payable in three installments annually, beginning June 26, 2020, with such installment payments accruing interest at a rate of 4% per year. As part of the Royalty Agreement, the Company and Metaswitch (i) have released the other from all claims and liabilities; (ii) have licensed each party's existing patent portfolio to the other party; and (iii) have requested the applicable courts to dismiss the Lawsuits. The Company received $37.5 million of aggregate payments from Metaswitch in the second quarter of 2019 and recorded notes receivable for future payments of $25.5 million, comprised of $8.5 million in Other current assets and $17.0 million in Other assets in the condensed consolidated balance sheets at both March 31, 2020 and December 31, 2019. Contingencies On November 8, 2018, Ron Miller, a purported stockholder of the Company, filed a Class Action Complaint (the "Miller Complaint") in the United States District Court for the District of Massachusetts (the "Massachusetts District Court") against the Company and three of its former officers (collectively, the "Defendants"), claiming to represent a class of purchasers of Sonus common stock during the period from January 8, 2015 through March 24, 2015 and alleging violations of the federal securities laws. Similar to a previous complaint entitled Sousa et al. vs. Sonus Networks, Inc. et al., which was dismissed with prejudice by an order dated June 6, 2017, the Miller Complaint claims that the Defendants made misleading forward-looking statements concerning Sonus' expected fiscal first quarter of 2015 financial performance, which statements were also the subject of an August 7, 2018 Securities and Exchange Commission Cease and Desist Order, whose findings the Company neither admitted nor denied. The Miller plaintiffs are seeking monetary damages. After the Miller Complaint was filed, several parties filed and briefed motions seeking to be selected by the Massachusetts District Court to serve as a Lead Plaintiff in the action. On June 21, 2019, the Massachusetts District Court appointed a group as Lead Plaintiffs and the Lead Plaintiffs filed an amended complaint on July 19, 2019. On August 30, 2019, the Defendants filed a motion to dismiss the Miller Complaint and, on October 4, 2019, the Lead Plaintiffs filed an opposition to the motion to dismiss. There was an oral argument on the motion to dismiss on February 12, 2020. In addition, the Company is often a party to disputes and legal proceedings that it considers routine and incidental to its business. Management does not expect the results of any of these actions to have a material effect on the Company's business or condensed consolidated financial statements.

BASIS OF PRESENTATION (Policies)	3 Months Ended
BASIS OF PRESENTATION (Policies)	Mar. 31, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation In the opinion of management, the accompanying unaudited condensed consolidated financial statements include all adjustments, consisting only of normal recurring items, necessary for their fair presentation with accounting principles generally accepted in the United States of America ("GAAP") and with the rules and regulations of the U.S. Securities and Exchange Commission ("SEC"). On March 3, 2020 (the "ECI Merger Date"), the Company merged with ECI Telecom Group Ltd. ("ECI") (the "ECI Merger"). The financial results of ECI are included in the Company's condensed consolidated financial statements for the period subsequent to the ECI Merger Date. On February 28, 2019 (the "Anova Acquisition Date"), the Company acquired the business and technology assets of Anova Data, Inc. ("Anova"). The financial results of Anova are included in the Company's condensed consolidated financial statements for the period subsequent to the Anova Acquisition Date. Interim results are not necessarily indicative of results for a full year or any future interim period. The information included in this Quarterly Report on Form 10-Q should be read in conjunction with the Company's Annual Report on Form 10-K for the year ended December 31, 2019 (the "Annual Report"), which was filed with the SEC on February 28, 2020.
Transfers of Financial Assets	Transfers of Financial Assets. The Company's recently acquired subsidiary, ECI Telecom Group Ltd. ("ECI"), maintains customer receivables factoring agreements with a number of financial institutions. Under the terms of these agreements, the Company may transfer receivables to the financial institutions, on a non-recourse basis, provided that the financial institutions approve the receivables in advance. The Company maintains credit insurance policies from major insurance providers or obtains letters of credit from the customers for a majority of its factored trade receivables. In some cases, the Company maintains some recourse obligations, limited to events of commercial disputes, such as product defects, which are not covered under the credit insurance policy, and are unrelated to the credit worthiness of the customer. The Company does not expect any recourse to take place in the foreseeable future due to commercial disputes. The Company accounts for the factoring of its financial assets as a sale of the assets and records the factoring fees, when incurred, as a component of interest expense in the condensed consolidated statements of operations and the proceeds from the sales of receivables are included in cash from operating activities in the condensed consolidated statements of cash flows.
Warranty	Warranty. The Company records warranty liabilities for estimated costs of fulfilling its obligations under standard limited hardware and software warranties at the time of sale. The liability for standard warranties is included in Accrued expenses and other and Other non-current liabilities in the condensed consolidated balance sheet at March 31, 2020. The specific warranty terms and conditions vary depending upon the country in which the Company does business, but generally includes material costs, technical support, labor and associated overhead over a period ranging from one to three years.
Principles of Consolidation	Principles of Consolidation The condensed consolidated financial statements include the accounts of Ribbon and its wholly-owned subsidiaries. Intercompany transactions and balances have been eliminated in consolidation.
Use of Estimates and Judgments	Use of Estimates and Judgments The preparation of financial statements in conformity with GAAP requires Ribbon to make estimates and assumptions that affect the reported amounts of assets and liabilities and disclosure of contingent assets and liabilities at the date of the financial statements and the reported amounts of revenue and expenses during the reporting periods. Significant estimates and judgments relied upon in preparing these condensed consolidated financial statements include accounting for business combinations, revenue recognition for multiple element arrangements, inventory valuations, assumptions used to determine the fair value of stock-based compensation, intangible asset and goodwill valuations, including impairments, legal contingencies and recoverability of Ribbon's net deferred tax assets and the related valuation allowances. Ribbon regularly assesses these estimates and records changes in estimates in the period in which they become known. Ribbon bases its estimates on historical experience and various other assumptions that it believes to be reasonable under the circumstances. Actual results could differ from those estimates.
Reclassifications	Reclassifications Certain reclassifications, not affecting previously reported net loss, have been made to the previously issued financial statements to conform to the current period presentation.
Restricted Cash	Restricted Cash The Company classifies as restricted cash all cash pledged as collateral to secure long-term obligations and all cash whose use is otherwise limited by contractual provisions.
Fair Value of Financial Instruments	Fair Value of Financial Instruments The carrying amounts of the Company's financial instruments approximate their fair values and include cash equivalents, accounts receivable, borrowings under a revolving credit facility, accounts payable and long-term debt.
Operating Segments	Operating Segments The Company currently operates in a single segment, as the chief operating decision maker made decisions and assessed performance at the company level. The Company's chief operating decision maker is its President and Chief Executive Officer, who began his employment with the Company effective March 1, 2020. From January 1, 2020 to March 1, 2020, the Company's chief operating decision makers were its former Interim Co-Presidents and Chief Executive Officers. Operating segments are identified as components of an enterprise about which separate discrete financial information is utilized for evaluation by the chief operating decision maker in making decisions regarding resource allocation and assessing performance. To date, the chief operating decision maker has made such decisions and assessed performance at the company level as one segment. However, with the acquisition of ECI, the Company's chief operating decision maker is currently assessing the appropriate separate discrete financial information he will utilize for making such decisions. Accordingly, the Company is reporting one operating segment for the three months ended March 31, 2020.
Fair Value Hierarchy	Fair Value Hierarchy Fair value is the price that would be received to sell an asset or paid to transfer a liability in an orderly transaction between market participants. As such, fair value is a market-based measurement that should be determined based on assumptions that market participants would use in pricing an asset or a liability. The three-tier fair value hierarchy is based on the level of independent, objective evidence surrounding the inputs used to measure fair value. A financial instrument's categorization within the fair value hierarchy is based upon the lowest level of input that is significant to the fair value measurement. The fair value hierarchy is as follows: Level 1. Level 1 applies to assets or liabilities for which there are quoted prices in active markets for identical assets or liabilities. Level 2. Level 2 applies to assets or liabilities for which there are inputs that are directly or indirectly observable in the marketplace, such as quoted prices for similar assets or liabilities in active markets or quoted prices for identical assets or liabilities in markets with insufficient volume or infrequent transactions (less active markets). Level 3. Level 3 applies to assets or liabilities for which there are unobservable inputs to the valuation methodology that are significant to the measurement of the fair value of the assets or liabilities.
Recent Accounting Pronouncements	Recent Accounting Pronouncements The Financial Accounting Standards Board ("FASB") has issued the following accounting pronouncements, all of which became effective for the Company in 2020 and none of which had a material impact on the Company's condensed consolidated financial statements: In March 2020, the FASB issued Accounting Standards Update ("ASU") 2020-04, Reference Rate Reform (Topic 848): Facilitation of the Effects of Reference Rate Reform on Financial Reporting ("ASU 2020-04"), which provides optional expedients and exceptions for applying generally accepted accounting principles to contract modifications and hedging relationships, subject to meeting certain criteria that reference LIBOR or another reference rate expected to be discontinued. In March 2020, the FASB issued ASU 2020-03, Codification Improvements to Financial Instruments ("ASU 2020-03"), which makes narrow-scope amendments related to topics regarding fair value option disclosures, applicability of the portfolio exception in Accounting Standards Codification ("ASC") 820 to nonfinancial items, disclosures for depository and lending institutions, cross reference to guidance in ASC 470-50 on line of credit or revolving debt arrangements, cross reference to net asset value practical expedient in ASC 820-10, interaction between ASC 842 and ASC 326 and between ASC 326 and ASC 860-20. In August 2018, the FASB issued ASU 2018-15, Intangibles - Goodwill and Other - Internal-Use Software (Subtopic 350-40): Customer’s Accounting for Implementation Costs Incurred in a Cloud Computing Arrangement That Is a Service Contract (“ASU 2018-15”), which provides guidance on implementation costs incurred in a cloud computing arrangement (“CCA”) that is a service contract. ASU 2018-15 amends ASC 350, Intangibles - Goodwill and Other (“ASC 350”) to include in its scope implementation costs of a CCA that is a service contract and clarifies that a customer should apply the guidance in ASC 350-40 to determine which implementation costs should be capitalized in such a CCA. In August 2018, the FASB issued ASU 2018-14, Compensation - Retirement Benefits - Defined Benefit Plans - General (Subtopic 715-20): Disclosure Framework - Changes to the Disclosure Requirements for Defined Benefit Plans (“ASU 2018-14”), which amends ASC 715, Compensation - Retirement Benefits, to add, remove and clarify disclosure requirements related to defined benefit pension and other postretirement plans. In August 2018, the FASB issued ASU 2018-13, Fair Value Measurement (Topic 820): Disclosure Framework - Changes to the Disclosure Requirements for Fair Value Measurement (“ASU 2018-13”), which changes the fair value measurement requirements of ASC 820, Fair Value Measurement. In June 2016, the FASB issued ASU 2016-13, Financial Instruments - Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments ("ASU 2016-13"), which adds an impairment model that is based on expected losses rather than incurred losses. Under ASU 2016-13, an entity recognizes as an allowance its estimate of expected credit losses, which the FASB believes will result in more timely recognition of such losses. In April and May 2019, the FASB issued ASU 2019-04, Codification Improvements to Topic 326, Financial Instruments - Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments ("ASU 2019-04") and ASU 2019-05 Financial Instruments - Credit Losses (Topic 326): Targeted Transition Relief ("ASU 2019-05"), respectively. ASU 2019-04 provides transition relief for entities adopting ASU 2016-13 and ASU 2019-05 clarifies certain aspects of the accounting for credit losses, hedging activities and financial instruments in connection with the adoption of ASU 2016-13. The FASB has issued the following accounting pronouncement which becomes effective for the Company in 2021, which the Company does not believe will have a material impact on its condensed consolidated financial statements upon adoption: In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes ("ASU 2019-12"), which modifies ASC 740 to simplify the accounting for income taxes. ASU 2019-12 addresses the accounting for hybrid tax regimes, tax basis step-up in goodwill obtained in a transaction that is not a business combination, separate financial statements of legal entities not subject to tax, intraperiod tax allocation exception to incremental approach, ownership changes in investments - changes from a subsidiary to an equity method investment, ownership changes in investments - changes from an equity method investment to a subsidiary, interim period accounting for enacted changes in tax law and year-to-date loss limitation in interim period tax accounting.
Revenue Recognition	The Company accounts for revenue in accordance with ASC 606, Revenue from Contracts with Customers ("ASC 606"), which it adopted on January 1, 2018 using the modified retrospective method. The Company derives revenues from two primary sources: products and services. Product revenue includes the Company's hardware and software that function together to deliver the products' essential functionality. Software and hardware are also sold on a standalone basis. Services include customer support (software updates, upgrades and technical support), consulting, design services, installation services and training. Generally, contracts with customers contain multiple performance obligations, consisting of products and services. For these contracts, the Company accounts for individual performance obligations separately if they are considered distinct. When an arrangement contains more than one performance obligation, the Company will generally allocate the transaction price to each performance obligation on a relative standalone selling price basis. The best evidence of a standalone selling price is the observable price of a good or service when the entity sells that good or service separately in similar circumstances and to similar customers. If the good or service is not sold separately, an entity must estimate the standalone selling price by using an approach that maximizes the use of observable inputs. Acceptable estimation methods include but are not limited to: (1) adjusted market assessment; (2) expected cost plus a margin; and (3) a residual approach (when the standalone selling price is not directly observable and is either highly variable or uncertain). The Company's software licenses typically provide a perpetual right to use the Company's software. The Company also sells term-based software licenses that expire and Software-as-a-Service ("SaaS")-based software which are referred to as subscription arrangements. The Company does not customize its software nor are installation services required, as the customer has a right to utilize internal resources or a third-party service company. The software and hardware are delivered before related services are provided and are functional without professional services or customer support. The Company has concluded that its software licenses are functional intellectual property that are distinct, as the user can benefit from the software on its own. The product revenue is typically recognized upon transfer of control or when the software is made available for download, as this is the point that the user of the software can direct the use of, and obtain substantially all of the remaining benefits from, the functional intellectual property. The Company does not recognize software revenue related to the renewal of subscription software licenses earlier than the beginning of the subscription period. Hardware product is generally sold with software to provide the customer solution. Services revenue includes revenue from customer support and other professional services. The Company offers warranties on its products. Certain of the Company's warranties are considered to be assurance-type in nature and do not cover anything beyond ensuring that the product is functioning as intended. Based on the guidance in ASC 606, assurance-type warranties do not represent separate performance obligations. The Company also sells separately-priced maintenance service contracts, which qualify as service-type warranties and represent separate performance obligations. The Company does not allow and has no history of accepting product returns. Customer support includes software updates on a when-and-if-available basis, telephone support, integrated web-based support and bug fixes or patches. The Company sells its customer support contracts at a percentage of list or net product price related to the support. Customer support revenue is recognized ratably over the term of the customer support agreement, which is typically one year. The Company's professional services include consulting, technical support, resident engineer services, design services and installation services. Because control transfers over time, revenue is recognized based on progress toward completion of the performance obligation. The method to measure progress toward completion requires judgment and is based on the nature of the products or services to be provided. The Company generally uses the input method to measure progress for its contracts because it believes such method best depicts the transfer of assets to the customer, which occurs as the Company incurs costs for the contracts. Under the cost-to-cost measure of progress, the progress toward completion is measured based on the ratio of costs incurred to date to the total estimated costs at completion of the performance obligation. When the measure of progress is based upon expended labor, progress toward completion is measured as the ratio of labor time expended to date versus the total estimated labor time required to complete the performance obligation. Revenue is recorded proportionally as costs are incurred or labor is expended. Costs to fulfill these obligations include internal labor as well as subcontractor costs. Customer training includes courses offered by the Company. The related revenue is typically recognized as the training services are performed.

BUSINESS ACQUISITIONS (Tables)

3 Months Ended

Mar. 31, 2020

Business Combinations [Abstract]

Summary of preliminary allocation of purchase consideration

A summary of the preliminary allocation of the purchase consideration for ECI is as follow (in thousands):



Fair value of consideration transferred:
Cash consideration:
Repayment of ECI outstanding debt obligations	$	183,266
Cash paid to selling shareholders	139,244
Payment to selling shareholders from sale of ECI real estate assets	33,400
Less cash and restricted cash acquired	(9,058		)
Net cash consideration	346,852
Fair value of Ribbon stock issued	108,550
Fair value of total consideration	$	455,402

Fair value of assets acquired and liabilities assumed:
Current assets, net of cash and restricted cash acquired	$	131,447
Property and equipment	55,207
Intangible assets:
In-process research and development	31,000
Developed technology	106,900
Customer relationships	114,000
Trade names	2,000
Goodwill	189,493
Other noncurrent assets	56,204
Deferred revenue	(7,731		)
Other current liabilities	(143,873		)
Deferred revenue, net of current	(6,641		)
Deferred tax liability	(13,308		)
Other long-term liabilities	(59,296		)
	$	455,402

Unaudited pro forma results



	Three months ended
	March 31, 2020			March 31, 2019
Revenue	$	183,189		$	208,947
Net loss	$	(39,129	)	$	(63,699	)
Loss per share	$	(0.25	)	$	(0.45	)

Schedule of components of acquisition related costs

The Company's acquisition- and integration-related expenses for the three months ended March 31, 2020 and 2019 were as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019
Professional and services fees (acquisition-related)	$	12,374	$	1,505
Integration-related expenses	10		1,694
	$	12,384	$	3,199

EARNINGS (LOSS) PER SHARE (Tables)

3 Months Ended

Mar. 31, 2020

Earnings Per Share [Abstract]

Schedule of calculations of shares used to compute basic and diluted earnings (loss) per share

The calculations of shares used to compute earnings (loss) per share were as follows (in thousands):



	Three months ended
	March 31, 2020	March 31, 2019
Weighted average shares outstanding—basic	120,992	108,167
Potential dilutive common shares	—	—
Weighted average shares outstanding—diluted	120,992	108,167

INVENTORY (Tables)

3 Months Ended

Mar. 31, 2020

Inventory Disclosure [Abstract]

Schedule of inventory

Inventory at March 31, 2020 and December 31, 2019 consisted of the following (in thousands):



	March 31, 2020			December 31, 2019
On-hand final assemblies and finished goods inventories	$	71,964		$	13,283
Deferred cost of goods sold	4,167			2,441
	76,131			15,724
Less noncurrent portion (included in other assets)	(9,064		)	(924		)
Current portion	$	67,067		$	14,800

INTANGIBLE ASSETS AND GOODWILL (Tables)

3 Months Ended

Mar. 31, 2020

Goodwill and Intangible Assets Disclosure [Abstract]

Schedule of intangible assets

The Company's intangible assets at March 31, 2020 and December 31, 2019 consisted of the following (in thousands):



March 31, 2020	Weighted average amortization period (years)	Cost		Accumulated amortization		Net carrying value
In-process research and development	*	$	36,600	$	—	$	36,600
Developed technology	7.92	295,780		109,714		186,066
Customer relationships	11.83	266,140		38,507		227,633
Trade names	3.60	4,000		1,369		2,631
Internal use software	3.00	730		730		—
	9.13	$	603,250	$	150,320	$	452,930



December 31, 2019	Weighted average amortization period (years)	Cost		Accumulated amortization		Net carrying value
In-process research and development	*	$	5,600	$	—	$	5,600
Developed technology	6.79	188,880		100,760		88,120
Customer relationships	9.46	152,140		33,350		118,790
Trade names	5.20	2,000		1,144		856
Internal use software	3.00	730		730		—
	7.82	$	349,350	$	135,984	$	213,366

* An in-process research and development intangible asset has an indefinite life until the product is generally available, at which time such asset is typically reclassified to developed technology.

Schedule of amortization expense related to intangible assets

Amortization expense for intangible assets for the three months ended March 31, 2020 and 2019 was as follows (in thousands):



	Three months ended				Statement of operations classification
	March 31, 2020		March 31, 2019		Statement of operations classification
Developed technology	$	8,954	$	9,645	Cost of revenue - product
Customer relationships	5,156		2,130		Sales and marketing
Trade names	224		147		Sales and marketing
	$	14,334	$	11,922

Schedule of estimated future amortization expense for intangible assets

Estimated future amortization expense for the Company's intangible assets at March 31, 2020 was as follows (in thousands):



Years ending December 31,
Remainder of 2020	$	44,869
2021	64,323
2022	58,153
2023	51,445
2024	43,477
Thereafter	190,663
	$	452,930

Schedule of goodwill

The changes in the carrying value of the Company's goodwill in the three months ended March 31, 2020 and 2019 were as follows (in thousands):




Balance at January 1	2020			2019
Goodwill	$	392,302		$	386,761
Accumulated impairment losses	(167,406		)	(3,106		)
	224,896			383,655
Acquisition of ECI	189,493			—
Acquisition of Anova	—			5,541
Balance at March 31	$	414,389		$	389,196

Balance at March 31
Goodwill	$	581,795		$	392,302
Accumulated impairment losses	(167,406		)	(3,106		)
	$	414,389		$	389,196

ACCRUED EXPENSES (Tables)

3 Months Ended

Mar. 31, 2020

Payables and Accruals [Abstract]

Schedule of accrued expenses

Accrued expenses at March 31, 2020 and December 31, 2019 consisted of the following (in thousands):



	March 31, 2020		December 31, 2019
Employee compensation and related costs	$	51,718	$	27,166
Professional fees	12,875		13,331
Taxes payable	18,424		842
Other	53,002		15,361
	$	136,019	$	56,700

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES (Tables)

3 Months Ended

Mar. 31, 2020

Restructuring and Related Activities [Abstract]

Summary of restructuring accrual activity

The components of Restructuring and related expense for the three months ended March 31, 2020 and 2019 were as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019
Severance and related costs	$	1,771	$	4,919
Variable and other facilities-related costs	234		13
Accelerated amortization of lease assets due to cease-use	70		—
	$	2,075	$	4,932

A summary of the 2019 Restructuring Initiative accrual activity for severance and related costs for the three months ended March 31, 2020 is as follows (in thousands):



	Balance at January 1, 2020		Initiatives charged to expense		Reclassify accelerated amortization to operating lease liabilities			Cash payments			Balance at March 31, 2020
Severance	$	2,110	$	655	$	—		$	(1,253	)	$	1,512
Facilities	991		304		(70		)	(272		)	953
	$	3,101	$	959	$	(70	)	$	(1,525	)	$	2,465

A summary of the GENBAND Merger Restructuring Initiative accrual activity for the three months ended March 31, 2020 is as follows (in thousands):



	Balance at January 1, 2020		Cash payments			Balance at March 31, 2020
Severance	$	409	$	(351	)	$	58

WARRANTY ACCRUALS (Tables)

3 Months Ended

Mar. 31, 2020

Guarantees and Product Warranties [Abstract]

Changes in accrual balance

The changes in the Company's accrual balance in the three months ended March 31, 2020 were as follows (in thousands):



Balance at January 1, 2020	$	—
Assumed liability in connection with ECI Merger	15,706
Current period provisions	502
Settlements	(528		)
Balance at March 31, 2020	$	15,680

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES (Tables)

3 Months Ended

Mar. 31, 2020

Derivative Instruments and Hedging Activities Disclosure [Abstract]

Impact of derivative financial instrument on condensed consolidated statement of operations

The impact of the Company’s derivative financial instrument on its condensed consolidated statement of comprehensive loss for the three months ended March 31, 2020 was as follows (in thousands):



Loss recognized in other comprehensive loss on derivative (effective portion)	$	(9,717	)
Amount reclassified from accumulated other comprehensive loss to interest expense (effective portion)	$	190

Fair values and locations in the condensed consolidated balance sheet



	Balance sheet location
Interest rate derivative - liability derivative	Accrued expenses and other	$	(238	)
Interest rate derivative - liability derivative	Other long-term liabilities	$	(9,289	)

REVENUE RECOGNITION (Tables)

3 Months Ended

Mar. 31, 2020

Revenue from Contract with Customer [Abstract]

Schedule of Timing of Performance Obligation

The Company's typical performance obligations include the following:



Performance Obligation	When Performance Obligation is Typically Satisfied	When Payment is Typically Due
Software and Product Revenue
Software licenses (perpetual or term)	Upon transfer of control; typically, when made available for download (point in time)	Generally, within 30 days of invoicing except for term licenses, which may be paid for over time

Software licenses (subscription)	Upon activation of hosted site (over time)	Generally, within 30 days of invoicing

Appliances	When control of the appliance passes to the customer; typically, upon delivery (point in time)	Generally, within 30 days of invoicing

Software upgrades	Upon transfer of control; typically, when made available for download (point in time)	Generally, within 30 days of invoicing

Customer Support Revenue
Customer support	Ratably over the course of the support contract (over time)	Generally, within 30 days of invoicing

Professional Services
Other professional services (excluding training services)	As work is performed (over time)	Generally, within 30 days of invoicing (upon completion of services)

Training	When the class is taught (point in time)	Generally, within 30 days of services being performed

Disaggregation of Revenue

The Company's revenue for the three months ended March 31, 2020 and 2019 was disaggregated as follows:



Three months ended March 31, 2020	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	36,365	$	31,466	$	10,566	$	78,397
Europe, Middle East and Africa	20,365		14,810		4,015		39,190
Japan	4,952		2,874		2,614		10,440
Asia Pacific	9,991		4,637		2,264		16,892
Other	4,226		7,281		1,556		13,063
	$	75,899	$	61,068	$	21,015	$	157,982



Three months ended March 31, 2019	Product revenue		Service revenue (maintenance)		Service revenue (professional services)		Total revenue
United States	$	28,446	$	32,787	$	7,343	$	68,576
Europe, Middle East and Africa	6,458		10,723		2,849		20,030
Japan	3,961		2,913		1,562		8,436
Asia Pacific	4,675		3,663		869		9,207
Other	3,940		6,903		1,836		12,679
	$	47,480	$	56,989	$	14,459	$	118,928



	Three months ended
	March 31, 2020		March 31, 2019
Indirect sales through channel partner program	$	28,604	$	19,174
Direct sales	47,295		28,306
	$	75,899	$	47,480

The Company's product revenue from sales to enterprise customers and from sales to service provider customers for the three months ended March 31, 2020 and 2019 was as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019
Sales to enterprise customers	$	27,281	$	14,755
Sales to service provider customers	48,618		32,725
	$	75,899	$	47,480

Schedule of Customer Assets and Liabilities

The changes in the Company's accounts receivable, unbilled receivables and deferred revenue balances for the three months ended March 31, 2020 were as follows (in thousands):



	Accounts receivable		Unbilled accounts receivable		Deferred revenue (current)		Deferred revenue (long-term)
Balance at January 1, 2020	$	168,502	$	24,204	$	100,406	$	20,482
Increase (decrease), net	1,286		11,801		13,293		5,429
Balance at March 31, 2020	$	169,788	$	36,005	$	113,699	$	25,911

STOCK-BASED COMPENSATION PLANS (Tables)

3 Months Ended

Mar. 31, 2020

Share-based Payment Arrangement [Abstract]

Schedule of activity related to outstanding stock options

The activity related to the Company's outstanding stock options for the three months ended March 31, 2020 was as follows:



	Number of Shares		Weighted Average Exercise Price		Weighted Average Remaining Contractual Term (years)	Aggregate Intrinsic Value (in thousands)
Outstanding at January 1, 2020	297,124		$	11.55
Granted	—		$	—
Exercised	(3,014	)	$	1.74
Forfeited	(1,470	)	$	1.80
Expired	(4,920	)	$	18.10
Outstanding at March 31, 2020	287,720		$	11.59	4.33	$	109
Vested or expected to vest at March 31, 2020	285,559		$	11.66	4.31	$	108
Exercisable at March 31, 2020	260,307		$	12.58	4.03	$	85

Schedule of stock options, additional information

Additional information regarding the Company's stock options for the three months ended March 31, 2020 was as follows (in thousands):



Total intrinsic value of stock options exercised	$	5
Cash received from the exercise of stock options	$	5

Schedule of activity related to unvested restricted stock grants

The activity related to the Company's RSAs for the three months ended March 31, 2020 was as follows:



	Shares		Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2020	487,976		$	6.87
Granted	—		$	—
Vested	(89,920	)	$	7.04
Forfeited	(4,499	)	$	7.04
Unvested balance at March 31, 2020	393,557		$	6.83

The activity related to the Company's RSUs for the three months ended March 31, 2020 was as follows:



	Shares		Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2020	2,790,060		$	5.11
Granted	4,123,151		$	2.22
Vested	(927,062	)	$	4.81
Forfeited	(237,818	)	$	4.69
Unvested balance at March 31, 2020	5,748,331		$	3.10

Schedule of activity related to performance stock awards

The activity related to the Company's PSUs for the three months ended March 31, 2020 was as follows:



	Shares		Weighted Average Grant Date Fair Value
Unvested balance at January 1, 2020	1,067,073		$	5.94
Granted	4,847,500		$	2.23
Vested	(315,866	)	$	5.53
Forfeited	(359,777	)	$	5.51
Unvested balance at March 31, 2020	5,238,930		$	2.52

Schedule of stock-based compensation expenses which are included in condensed consolidated statement of operations

The condensed consolidated statements of operations include stock-based compensation for the three months ended March 31, 2020 and 2019 as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019
Product cost of revenue	$	27	$	14
Service cost of revenue	130		92
Research and development	558		507
Sales and marketing	752		984
General and administrative	1,509		2,542
	$	2,976	$	4,139

MAJOR CUSTOMERS (Tables)

3 Months Ended

Mar. 31, 2020

Risks and Uncertainties [Abstract]

Schedule of customers contributing 10% or more of the revenue

The following customers contributed 10% or more of the Company's revenue in the three months ended March 31, 2020 and 2019:



	Three months ended
	March 31, 2020	March 31, 2019
Verizon Communications Inc.	13%	15%
AT&T Inc.	10%	10%

LEASES (Tables)

3 Months Ended

Mar. 31, 2020

Leases [Abstract]

Right-of-use lease assets and lease liabilities

The Company's right-of-use lease assets and lease liabilities at March 31, 2020 and December 31, 2019 were as follows (in thousands):



	Classification	March 31, 2020		December 31, 2019
Assets
Operating lease assets	Operating lease right-of-use assets	$	66,295	$	36,654
Finance lease assets*	Property and equipment, net	2,093		2,420
Total leased assets		$	68,388	$	39,074

Liabilities
Current
Operating	Operating lease liabilities	$	18,201	$	7,719
Finance	Accrued expenses and other	1,376		1,005
Noncurrent
Operating	Operating lease liabilities, net of current	55,857		37,202
Finance	Other long-term liabilities	1,436		2,144
Total lease liabilities		$	76,870	$	48,070

* Finance lease assets were recorded net of accumulated depreciation of $2.3 million and $2.0 million at March 31, 2020 and December 31, 2019, respectively.

Components of lease expense

The components of lease expense for the three months ended March 31, 2020 and 2019 were as follows (in thousands):



	Three months ended
	March 31, 2020		March 31, 2019

Operating lease cost*	$	3,344	$	2,441
Finance lease cost
Amortization of leased assets	319		244
Interest on lease liabilities	55		64
Short-term lease cost	5,523		4,671
Variable lease costs (costs excluded from minimum fixed lease payments)	637		601
Net lease cost	$	9,878	$	8,021

Other information related to the Company's leases as of and for the three months ended March 31, 2020 and 2019 was as follows (in thousands, except lease terms and percentages):



	Three months ended
	March 31, 2020		March 31, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows for operating leases	$	3,113	$	2,355
Operating cash flows for finance leases	$	55	$	64
Financing cash flows for finance leases	$	338	$	230



	March 31, 2020		December 31, 2019
Weighted average remaining lease term (years)
Operating leases	5.36		6.73
Finance leases	2.19		2.35
Weighted average discount rate
Operating leases	5.58	%	6.50	%
Finance leases	7.49	%	7.54	%

Future minimum fixed lease payments under noncancelable finance leases

Future minimum fixed lease payments under noncancelable leases at March 31, 2020 and December 31, 2019 were as follows (in thousands):



	March 31, 2020
	Operating			Finance
	leases			leases
Remainder of 2020	$	16,251		$	1,214
2021	19,067			1,179
2022	15,345			587
2023	12,889			36
2024	6,692			—
2025 and beyond	16,127			—
Total lease payments	86,371			3,016
Less: interest	(12,313		)	(204		)
Present value of lease liabilities	$	74,058		$	2,812



	December 31, 2019
	Operating			Finance
	leases			leases
2020	$	10,290		$	1,644
2021	9,468			1,159
2022	7,665			581
2023	7,067			—
2024	5,303			—
2025 and beyond	15,738			—
Total lease payments	55,531			3,384
Less: interest	(10,610		)	(235		)
Present value of lease liabilities	$	44,921		$	3,149

Future minimum fixed lease payments under noncancelable operating leases

Future minimum fixed lease payments under noncancelable leases at March 31, 2020 and December 31, 2019 were as follows (in thousands):



	March 31, 2020
	Operating			Finance
	leases			leases
Remainder of 2020	$	16,251		$	1,214
2021	19,067			1,179
2022	15,345			587
2023	12,889			36
2024	6,692			—
2025 and beyond	16,127			—
Total lease payments	86,371			3,016
Less: interest	(12,313		)	(204		)
Present value of lease liabilities	$	74,058		$	2,812



	December 31, 2019
	Operating			Finance
	leases			leases
2020	$	10,290		$	1,644
2021	9,468			1,159
2022	7,665			581
2023	7,067			—
2024	5,303			—
2025 and beyond	15,738			—
Total lease payments	55,531			3,384
Less: interest	(10,610		)	(235		)
Present value of lease liabilities	$	44,921		$	3,149

BASIS OF PRESENTATION (Details) customer in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) segment customer	Dec. 31, 2019 USD ($)
Accounting Policies [Abstract]
Cash received from the sale of certain accounts receivable	$ 15,100
Interest expense	100
Product Warranty Liability [Line Items]
Liability for product warranties	15,680	$ 0
Accrued expenses and other	6,700
Other long-term liabilities	9,000
Restricted cash	$ 13,200
Number of operating segments \| segment	1
Number of customers (more than) \| customer	1
Number of reportable operating segments \| segment	1
Tax payment on certain fixed assets
Product Warranty Liability [Line Items]
Restricted cash	$ 8,400
Restricted short-term bank deposits
Product Warranty Liability [Line Items]
Restricted cash	$ 4,800
Minimum
Product Warranty Liability [Line Items]
Product warranty period	1 year
Maximum
Product Warranty Liability [Line Items]
Product warranty period	3 years

BUSINESS ACQUISITIONS - ECI Narrative (Details) - USD ($) shares in Millions		3 Months Ended
	Nov. 14, 2019	Mar. 31, 2020	Mar. 31, 2019
Business Acquisition [Line Items]
Net cash consideration		$ 346,852,000	$ 0
Term Loan Facility
Business Acquisition [Line Items]
Commitments from lender	$ 400,000,000
Revolving Credit Facility
Business Acquisition [Line Items]
Commitments from lender	100,000,000
ECI
Business Acquisition [Line Items]
Proceeds from sale of real estate assets	$ 33,400,000
Revenue		30,000,000
Net loss		3,300,000
ECI
Business Acquisition [Line Items]
Common stock to be issued (in shares)	32.5
Fair value of Ribbon stock issued	$ 108,600,000	108,550,000
Net cash consideration	322,500,000	346,852,000
Repayment of ECI outstanding debt obligations	183,300,000	183,266,000
Payment to selling shareholders	$ 139,200,000	139,244,000
Indemnification receivable		$ 5,700,000
Weighted average useful life of intangible assets (in years)	12 years 5 months 8 days

BUSINESS ACQUISITIONS - Summary of Preliminary Allocation of Purchase Consideration (Details) - USD ($) $ in Thousands		3 Months Ended
	Nov. 14, 2019	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019	Dec. 31, 2018
Cash consideration:
Net cash consideration		$ 346,852	$ 0
Fair value of assets acquired and liabilities assumed:
Goodwill		414,389	$ 389,196	$ 224,896	$ 383,655
ECI
Cash consideration:
Repayment of ECI outstanding debt obligations	$ 183,300	183,266
Cash paid to selling shareholders	139,200	139,244
Payment to selling shareholders from sale of ECI real estate assets		33,400
Less cash and restricted cash acquired		(9,058)
Net cash consideration	322,500	346,852
Fair value of Ribbon stock issued	$ 108,600	108,550
Fair value of total consideration		455,402
Fair value of assets acquired and liabilities assumed:
Current assets, net of cash and restricted cash acquired		131,447
Property and equipment		55,207
Goodwill		189,493
Other noncurrent assets		56,204
Deferred revenue		(7,731)
Other current liabilities		(143,873)
Deferred revenue, net of current		(6,641)
Deferred tax liability		(13,308)
Other long-term liabilities		(59,296)
Fair value of assets acquired and liabilities assumed		455,402
ECI \| In-process research and development
Fair value of assets acquired and liabilities assumed:
Intangible assets		31,000
ECI \| Developed technology
Fair value of assets acquired and liabilities assumed:
Intangible assets		106,900
ECI \| Customer relationships
Fair value of assets acquired and liabilities assumed:
Intangible assets		114,000
ECI \| Trade names
Fair value of assets acquired and liabilities assumed:
Intangible assets		$ 2,000

BUSINESS ACQUISITIONS - Unaudited Pro Forma Results (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Business Combinations [Abstract]
Revenue	$ 183,189	$ 208,947
Net loss	$ (39,129)	$ (63,699)
Loss per share (in dollars per share)	$ (0.25)	$ (0.45)

BUSINESS ACQUISITIONS - Anova Data Narrative (Details) - USD ($) $ in Thousands			3 Months Ended
	Mar. 04, 2020	Jan. 31, 2019	Mar. 31, 2020	Dec. 31, 2019	Mar. 31, 2019	Dec. 31, 2018
Business Acquisition [Line Items]
Shares of common stock issued as purchase consideration			$ 110,180		$ 15,186
Goodwill			414,389	$ 224,896	$ 389,196	$ 383,655
Anova Data, Inc.
Business Acquisition [Line Items]
Common stock to be issued (in shares)		2,900,000
Shares of common stock issued as purchase consideration		$ 15,200
Number of additional shares potentially issued (in number of shares)		330,000
Fair value of additional shares potentially issued		$ 1,700
Number of shares issued after post-closing adjustments (in shares)	316,551
Fair value of total consideration			16,900
Finite-lived intangibles			11,200
Weighted average useful life of intangible assets (in years)		6 years 3 months
Net assets acquired			100
Goodwill			$ 5,500

BUSINESS ACQUISITIONS - Summary of Acquisition Related Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Business Combinations [Abstract]
Professional and services fees (acquisition-related)	$ 12,374	$ 1,505
Integration-related expenses	10	1,694
Total	$ 12,384	$ 3,199

EARNINGS (LOSS) PER SHARE (Details) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Reconciliation of weighted average shares outstanding from basic to diluted
Weighted average shares outstanding—basic	120,992	108,167
Potential dilutive common shares	0	0
Weighted average shares outstanding—diluted	120,992	108,167
Options not included in computation of diluted loss per share (in shares)	11,700	4,500

INVENTORY (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
On-hand final assemblies and finished goods inventories	$ 71,964	$ 13,283
Deferred cost of goods sold	4,167	2,441
Gross inventory	76,131	15,724
Less noncurrent portion (included in other assets)	(9,064)	(924)
Current portion	$ 67,067	$ 14,800

INTANGIBLE ASSETS AND GOODWILL - Schedule of Intangible Assets and Amortization (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Intangible Assets And Goodwill
Weighted average amortization period (years)	9 years 1 month 16 days		7 years 9 months 25 days
Cost	$ 603,250		$ 349,350
Accumulated amortization	150,320		135,984
Net carrying value	452,930		213,366
Amortization expense	14,334	$ 11,922
Estimated future amortization expense for intangible assets
Remainder of 2020	44,869
2021	64,323
2022	58,153
2023	51,445
2024	43,477
Thereafter	190,663
Total	452,930
In-process research and development
Intangible Assets And Goodwill
Cost	36,600		5,600
Accumulated amortization	0		0
Net carrying value	$ 36,600		$ 5,600
Developed technology
Intangible Assets And Goodwill
Weighted average amortization period (years)	7 years 11 months 1 day		6 years 9 months 15 days
Cost	$ 295,780		$ 188,880
Accumulated amortization	109,714		100,760
Net carrying value	186,066		$ 88,120
Amortization expense	$ 8,954	9,645
Customer relationships
Intangible Assets And Goodwill
Weighted average amortization period (years)	11 years 9 months 28 days		9 years 5 months 16 days
Cost	$ 266,140		$ 152,140
Accumulated amortization	38,507		33,350
Net carrying value	227,633		$ 118,790
Amortization expense	$ 5,156	2,130
Trade names
Intangible Assets And Goodwill
Weighted average amortization period (years)	3 years 7 months 6 days		5 years 2 months 12 days
Cost	$ 4,000		$ 2,000
Accumulated amortization	1,369		1,144
Net carrying value	2,631		$ 856
Amortization expense	$ 224	$ 147
Internal use software
Intangible Assets And Goodwill
Weighted average amortization period (years)	3 years		3 years
Cost	$ 730		$ 730
Accumulated amortization	730		730
Net carrying value	$ 0		$ 0

INTANGIBLE ASSETS AND GOODWILL - Schedule of Changes in Carrying Value of Goodwill (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Goodwill [Roll Forward]
Goodwill, gross, beginning of period	$ 392,302	$ 386,761
Accumulated impairment losses, beginning of period	(167,406)	(3,106)
Goodwill. beginning of period	224,896	383,655
Goodwill, gross, end of period	581,795	392,302
Accumulated impairment losses, end of period	(167,406)	(3,106)
Goodwill, end of period	414,389	389,196
ECI
Goodwill [Roll Forward]
Acquisition	189,493	0
Goodwill, end of period	189,493
Anova Data, Inc.
Goodwill [Roll Forward]
Acquisition	0	$ 5,541
Goodwill, end of period	$ 5,500

ACCRUED EXPENSES (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Payables and Accruals [Abstract]
Employee compensation and related costs	$ 51,718	$ 27,166
Professional fees	12,875	13,331
Taxes payable	18,424	842
Other	53,002	15,361
Total	$ 136,019	$ 56,700

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020 USD ($) employee executive	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Restructuring Cost and Reserve [Line Items]
Restructuring and related	$ 2,075	$ 4,932
Accelerated rent amortization	70	0
Long-term portion of accrued restructuring			$ 900
ECI Executive Severance \| Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and related	$ 1,100
Number of positions eliminated \| executive	3
2019 Restructuring Initiative
Restructuring Cost and Reserve [Line Items]
Restructuring and related	$ 959
2019 Restructuring Initiative \| Severance
Restructuring Cost and Reserve [Line Items]
Restructuring and related	$ 655
Number of positions eliminated \| employee	5
2019 Restructuring Initiative \| Facilities
Restructuring Cost and Reserve [Line Items]
Restructuring and related	$ 304
Accelerated rent amortization	$ 100		$ 3,700
Merger Restructuring Initiative
Restructuring Cost and Reserve [Line Items]
Restructuring and related		$ 4,900
Number of positions eliminated \| employee	40

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES - Components of Restructuring Expense (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Restructuring and Related Activities [Abstract]
Severance and related costs	$ 1,771	$ 4,919
Variable and other facilities-related costs	234	13
Accelerated amortization of lease assets due to cease-use	70	0
Restructuring and related expense	$ 2,075	$ 4,932

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES - Accrual Activity for Severance and Related Costs (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Restructuring Reserve [Roll Forward]
Initiatives charged to expense	$ 2,075	$ 4,932
Facilities
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	900
Balance at the end of the period	900
2019 Restructuring Initiative
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	3,101
Initiatives charged to expense	959
Reclassify accelerated amortization to operating lease liabilities	(70)
Cash payments	(1,525)
Balance at the end of the period	2,465
2019 Restructuring Initiative \| Severance
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	2,110
Initiatives charged to expense	655
Reclassify accelerated amortization to operating lease liabilities	0
Cash payments	(1,253)
Balance at the end of the period	1,512
2019 Restructuring Initiative \| Facilities
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	991
Initiatives charged to expense	304
Reclassify accelerated amortization to operating lease liabilities	(70)
Cash payments	(272)
Balance at the end of the period	$ 953

RESTRUCTURING AND FACILITIES CONSOLIDATION INITIATIVES - Assumed Restructuring Initiative Rollforward (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Restructuring Reserve [Roll Forward]
Initiatives charged to expense	$ 2,075	$ 4,932
Merger Restructuring Initiative
Restructuring Reserve [Roll Forward]
Initiatives charged to expense		$ 4,900
Severance \| Merger Restructuring Initiative
Restructuring Reserve [Roll Forward]
Balance at the beginning of the period	409
Cash payments	(351)
Balance at the end of the period	$ 58

WARRANTY ACCRUALS - Changes in Accrual Balance (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Movement in Standard Product Warranty Accrual [Roll Forward]
Balance at January 1, 2020	$ 0
Assumed liability in connection with ECI Merger	15,706
Current period provisions	502
Settlements	(528)
Balance at March 31, 2020	$ 15,680

WARRANTY ACCRUALS - Narrative (Details) $ in Millions	Mar. 31, 2020 USD ($)
Guarantees and Product Warranties [Abstract]
Accrued expenses and other	$ 6.7
Other long-term liabilities	$ 9.0

DEBT - Credit Facilities (Details)			3 Months Ended
DEBT - Credit Facilities (Details)	Mar. 03, 2020 USD ($)	Apr. 29, 2019 USD ($)	Mar. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	Nov. 14, 2019 USD ($)	Dec. 21, 2017 USD ($)
Debt Instrument [Line Items]
Letters of credit outstanding			$ 33,300,000
2019 Credit Facility
Debt Instrument [Line Items]
Outstanding balance				$ 48,800,000
2020 Credit Agreement
Debt Instrument [Line Items]
Commitments from lender	$ 500,000,000
Default rate percentage	2.00%
Repayments over next twelve months			10,000,000
Repayments of principal in year two			20,000,000
Repayments of principal in year three			20,000,000
Repayments of principal in year four			20,000,000
Repayments of principal in last year			30,000,000
Repayments of principal on the maturity date			$ 300,000,000
Percentage of Consolidated Adjusted EBITDA	100.00%
Consolidated Net Leverage Ratio	2.75
2020 Credit Agreement \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.00%
2020 Credit Agreement \| LIBOR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	1.50%
2020 Credit Agreement \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	3.50%
2020 Credit Agreement \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
2020 Credit Agreement \| Prime Rate \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate	0.50%
2020 Credit Agreement \| Prime Rate \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate	2.50%
Revolving Credit Facility
Debt Instrument [Line Items]
Commitments from lender					$ 100,000,000
Revolving Credit Facility \| Line of Credit
Debt Instrument [Line Items]
Commitments from lender		$ 100,000,000				$ 100,000,000
Default rate percentage			2.00%
Revolving Credit Facility \| Line of Credit \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate			0.00%
Revolving Credit Facility \| Line of Credit \| LIBOR \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate			1.50%
Revolving Credit Facility \| Line of Credit \| LIBOR \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate			3.00%
Revolving Credit Facility \| Line of Credit \| Base Rate
Debt Instrument [Line Items]
Basis spread on variable rate			0.50%
Revolving Credit Facility \| Line of Credit \| Additional Applicable Margin \| Minimum
Debt Instrument [Line Items]
Basis spread on variable rate			0.50%
Revolving Credit Facility \| Line of Credit \| Additional Applicable Margin \| Maximum
Debt Instrument [Line Items]
Basis spread on variable rate			2.00%
Revolving Credit Facility \| 2019 Credit Facility
Debt Instrument [Line Items]
Principal amount		50,000,000
Increase commitment under debt instrument		$ 75,000,000
Revolving Credit Facility \| 2019 Credit Facility \| Line of Credit
Debt Instrument [Line Items]
Outstanding balance				$ 8,000,000
Debt interest rate				3.30%
Revolving Credit Facility \| 2020 Credit Agreement
Debt Instrument [Line Items]
Commitments from lender	$ 100,000,000
Debt interest rate			3.90%
Letter of Credit \| Line of Credit
Debt Instrument [Line Items]
Commitments from lender						15,000,000
Letter of Credit \| 2019 Credit Facility \| Line of Credit
Debt Instrument [Line Items]
Outstanding balance				$ 5,400,000
Debt interest rate				1.50%
Letter of Credit \| 2020 Credit Agreement
Debt Instrument [Line Items]
Commitments from lender	30,000,000
Debt interest rate			3.00%
Letters of credit outstanding			$ 5,600,000
Swingline loan \| Line of Credit
Debt Instrument [Line Items]
Commitments from lender						$ 15,000,000
Swingline loan \| 2020 Credit Agreement
Debt Instrument [Line Items]
Commitments from lender	20,000,000
Term Loan Facility
Debt Instrument [Line Items]
Commitments from lender					$ 400,000,000
Term Loan Facility \| 2020 Credit Agreement
Debt Instrument [Line Items]
Commitments from lender	$ 400,000,000
Outstanding balance			$ 400,000,000

DEBT - Short-Term Loans (Details) $ in Millions	Mar. 31, 2020 USD ($)
Debt Disclosure [Abstract]
Short-term loans	$ 3.5
Weighted average interest rate	3.97%

DEBT - Letters of Credit and Performance and Bid Bonds (Details) $ in Millions	Mar. 31, 2020 USD ($)
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 33.3
Cash collateral	4.7
Various Uncommitted Facilities
Line of Credit Facility [Line Items]
Letters of credit outstanding	27.7
2020 Credit Agreement \| Letter of Credit
Line of Credit Facility [Line Items]
Letters of credit outstanding	$ 5.6

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Narrative (Details) $ in Millions	Mar. 31, 2020 USD ($)
Derivative [Line Items]
Reclassified as an increase to interest expense over the next twelve months	$ 2.4
Interest Rate Swap
Derivative [Line Items]
Notional amount	400.0
2020 Credit Agreement \| Term Loan Facility
Derivative [Line Items]
Outstanding balance	$ 400.0
Fixed rate	0.904%
Level Two \| Interest Rate Swap
Derivative [Line Items]
Interest rate derivative - liability derivative	$ 9.5

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Impact of Derivative Financial Instrument on Condensed Consolidated Statement of Operations (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Loss recognized in other comprehensive loss on derivative (effective portion)	$ (9,717)
Amount reclassified from accumulated other comprehensive loss to interest expense (effective portion)	$ 190

DERIVATIVE INSTRUMENTS AND HEDGING ACTIVITIES - Fair Values and Locations in the Condensed Consolidated Balance Sheet (Details) - Interest Rate Swap $ in Thousands	Mar. 31, 2020 USD ($)
Accrued expenses and other
Derivative [Line Items]
Interest rate derivative - liability derivative	$ (238)
Other long-term liabilities
Derivative [Line Items]
Interest rate derivative - liability derivative	$ (9,289)

REVENUE RECOGNITION - Schedule of Disaggregation of Revenue (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Disaggregation of Revenue [Line Items]
Total revenue	$ 157,982	$ 118,928
Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	75,899	47,480
Product revenue \| Sales to enterprise customers
Disaggregation of Revenue [Line Items]
Total revenue	27,281	14,755
Product revenue \| Sales to service provider customers
Disaggregation of Revenue [Line Items]
Total revenue	48,618	32,725
Product revenue \| Indirect sales through channel partner program
Disaggregation of Revenue [Line Items]
Total revenue	28,604	19,174
Product revenue \| Direct sales
Disaggregation of Revenue [Line Items]
Total revenue	47,295	28,306
Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	61,068	56,989
Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	21,015	14,459
United States
Disaggregation of Revenue [Line Items]
Total revenue	78,397	68,576
United States \| Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	36,365	28,446
United States \| Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	31,466	32,787
United States \| Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	10,566	7,343
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenue	39,190	20,030
Europe, Middle East and Africa \| Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	20,365	6,458
Europe, Middle East and Africa \| Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	14,810	10,723
Europe, Middle East and Africa \| Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	4,015	2,849
Japan
Disaggregation of Revenue [Line Items]
Total revenue	10,440	8,436
Japan \| Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	4,952	3,961
Japan \| Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	2,874	2,913
Japan \| Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	2,614	1,562
Asia Pacific
Disaggregation of Revenue [Line Items]
Total revenue	16,892	9,207
Asia Pacific \| Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	9,991	4,675
Asia Pacific \| Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	4,637	3,663
Asia Pacific \| Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	2,264	869
Other
Disaggregation of Revenue [Line Items]
Total revenue	13,063	12,679
Other \| Product revenue
Disaggregation of Revenue [Line Items]
Total revenue	4,226	3,940
Other \| Service revenue (maintenance)
Disaggregation of Revenue [Line Items]
Total revenue	7,281	6,903
Other \| Service revenue (professional services)
Disaggregation of Revenue [Line Items]
Total revenue	$ 1,556	$ 1,836

REVENUE RECOGNITION - Schedule of Customer Assets & Liabilities (Details) $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($)
Accounts receivable
Beginning balance	$ 168,502
Increase (decrease), net	1,286
Ending balance	169,788
Unbilled accounts receivable
Beginning balance	24,204
Increase (decrease), net	11,801
Ending balance	36,005
Deferred revenue (current)
Beginning balance	100,406
Increase (decrease), net	13,293
Ending balance	113,699
Deferred revenue (long-term)
Beginning balance	20,482
Increase (decrease), net	5,429
Ending balance	$ 25,911

REVENUE RECOGNITION - Narrative (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue from Contract with Customer [Abstract]
Revenue recognized	$ 41.0	$ 33.0
Customer contract expected life (in years)	5 years
Deferred sales commissions capitalized	$ 3.6		$ 3.6
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2021-01-01
Revenue from Contract with Customer [Abstract]
Revenue recognized	$ 12.0
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2022-01-01
Revenue from Contract with Customer [Abstract]
Revenue recognized	$ 8.0
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation, period	1 year
Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date [Axis]: 2023-01-01
Revenue from Contract with Customer [Abstract]
Revenue recognized	$ 6.0
Disaggregation of Revenue [Line Items]
Revenue, remaining performance obligation, period

COMMON STOCK REPURCHASES (Details) - Repurchase Program - USD ($)	Mar. 31, 2020	Jun. 30, 2019
Class of Stock [Line Items]
Repurchase amount authorized (up to)		$ 75,000,000
Remaining authorized repurchase amount	$ 70,500,000

STOCK-BASED COMPENSATION PLANS - Executive Equity Arrangements (Details) - USD ($) $ / shares in Units, $ in Millions		1 Months Ended		2 Months Ended	3 Months Ended
	Mar. 16, 2020	Mar. 31, 2020	May 31, 2018	Apr. 30, 2019	Mar. 31, 2020	Dec. 31, 2019
RSUs
Stock-based compensation
Eligible to vest (in shares)	462,963	5,748,331			5,748,331	2,790,060
Fair market value on date of grant	$ 1.0
Maximum number of shares to be settled (in shares)	4,750,000
Granted (in shares)					4,123,151
Vested (in shares)					927,062
Grant date fair value (in dollars per share)		$ 3.10			$ 3.10	$ 5.11
PSUs
Stock-based compensation
Eligible to vest (in shares)		5,238,930			5,238,930	1,067,073
Granted (in shares)				872,073	4,847,500
Vested (in shares)					315,866
Grant date fair value (in dollars per share)		$ 2.52			$ 2.52	$ 5.94
PSUs \| Market PSUs
Stock-based compensation
Granted (in shares)				348,829
Percent of performance metrics achieved					200.00%
Performance period (in years)					3 years
PSUs \| Performance PSUs
Stock-based compensation
Granted (in shares)				523,244
Achievement level (as a percentage)		30.493%
Percent of performance metrics achieved					200.00%
PSUs \| 2018 Performance Share Units
Stock-based compensation
Grant date fair value (in dollars per share)		$ 2.16			$ 2.16
PSUs \| Executives \| 2018 Performance Share Units
Stock-based compensation
Granted (in shares)			195,000
Percent of performance metrics achieved			150.00%
Vested (in shares)			292,500

STOCK-BASED COMPENSATION PLANS - Stock Options (Details) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2020 USD ($) $ / shares shares
Number of Shares
Outstanding at the beginning of the period (in shares) \| shares	297,124
Granted (in shares) \| shares	0
Exercised (in shares) \| shares	(3,014)
Forfeited (in shares) \| shares	(1,470)
Expired (in shares) \| shares	(4,920)
Outstanding at the end of the period (in shares) \| shares	287,720
Vested or expected to vest (in shares) \| shares	285,559
Exercisable (in shares) \| shares	260,307
Weighted Average Exercise Price
Outstanding at the beginning of the period (in dollars per share) \| $ / shares	$ 11.55
Granted (in dollars per share) \| $ / shares	0.00
Exercised (in dollars per share) \| $ / shares	1.74
Forfeited (in dollars per share) \| $ / shares	1.80
Expired (in dollars per share) \| $ / shares	18.10
Outstanding at the end of the period (in dollars per share) \| $ / shares	11.59
Vested or expected to vest (in dollars per share) \| $ / shares	11.66
Exercisable (in dollars per share) \| $ / shares	$ 12.58
Weighted Average Remaining Contractual Term (years)
Outstanding	4 years 4 months
Vested or expected to vest	4 years 3 months 22 days
Exercisable	4 years 12 days
Aggregate Intrinsic Value (in thousands)
Outstanding (in dollars) \| $	$ 109
Vested or expected to vest (in dollars) \| $	108
Exercisable (in dollars) \| $	85
Total intrinsic values of stock options exercised (in dollars) \| $	5
Cash received from the exercise of stock options (in dollars) \| $	$ 5

STOCK-BASED COMPENSATION PLANS - Restricted Stock Awards and Units and Performance-Based Stock Units (Details) - USD ($) $ / shares in Units, $ in Thousands	2 Months Ended	3 Months Ended
	Apr. 30, 2019	Mar. 31, 2020	Mar. 31, 2019
Weighted Average Grant Date Fair Value
Total grant date fair value of shares that vested during the period		$ 3,182	$ 4,334
RSAs
Shares
Unvested balance at the beginning of the period (in shares)		487,976
Granted (in shares)		0
Vested (in shares)		(89,920)
Forfeited (in shares)		(4,499)
Unvested balance at the end of the period (in shares)		393,557
Weighted Average Grant Date Fair Value
Unvested balance at the end of the period (in dollars per share)		$ 6.87
Granted (in dollars per share)		0.00
Vested (in dollars per share)		7.04
Forfeited (in dollars per share)		7.04
Unvested balance at end of the period (in dollars per share)		$ 6.83
Total grant date fair value of shares that vested during the period		$ 5,100
RSUs
Shares
Unvested balance at the beginning of the period (in shares)		2,790,060
Granted (in shares)		4,123,151
Vested (in shares)		(927,062)
Forfeited (in shares)		(237,818)
Unvested balance at the end of the period (in shares)		5,748,331
Weighted Average Grant Date Fair Value
Unvested balance at the end of the period (in dollars per share)		$ 5.11
Granted (in dollars per share)		2.22
Vested (in dollars per share)		4.81
Forfeited (in dollars per share)		4.69
Unvested balance at end of the period (in dollars per share)		$ 3.10
PSUs
Shares
Unvested balance at the beginning of the period (in shares)		1,067,073
Granted (in shares)	872,073	4,847,500
Vested (in shares)		(315,866)
Forfeited (in shares)		(359,777)
Unvested balance at the end of the period (in shares)		5,238,930
Weighted Average Grant Date Fair Value
Unvested balance at the end of the period (in dollars per share)		$ 5.94
Granted (in dollars per share)		2.23
Vested (in dollars per share)		5.53
Forfeited (in dollars per share)		5.51
Unvested balance at end of the period (in dollars per share)		$ 2.52
Total grant date fair value of shares that vested during the period		$ 1,700

STOCK-BASED COMPENSATION PLANS - Employee Stock Purchase Plan (Details) - ESPP	3 Months Ended
	Mar. 31, 2020 shares
Stock-based compensation
Offering period (in months)	6 months
Purchase price of common stock (percentage)	85.00%
Maximum number of shares purchasable per employee (in shares)	500

STOCK-BASED COMPENSATION PLANS - Stock-Based Compensation (Details) - USD ($)	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Stock-based compensation
Stock-based compensation	$ 2,976,000	$ 4,139,000
Tax benefit from stock based compensation expense	0	0
Fair value of the assumed awards attributable to future stock-based compensation expense	$ 26,300,000
Expected period for unrecognized expense	3 years
Product cost of revenue
Stock-based compensation
Stock-based compensation	$ 27,000	14,000
Service cost of revenue
Stock-based compensation
Stock-based compensation	130,000	92,000
Research and development
Stock-based compensation
Stock-based compensation	558,000	507,000
Sales and marketing
Stock-based compensation
Stock-based compensation	752,000	984,000
General and administrative
Stock-based compensation
Stock-based compensation	$ 1,509,000	$ 2,542,000

MAJOR CUSTOMERS (Details) - Customer	3 Months Ended		12 Months Ended
MAJOR CUSTOMERS (Details) - Customer	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Revenue \| Verizon Communications Inc.
MAJOR CUSTOMERS
Concentration risk, percentage	13.00%	15.00%
Revenue \| AT&T Inc.
MAJOR CUSTOMERS
Concentration risk, percentage	10.00%	10.00%
Accounts receivable balance
MAJOR CUSTOMERS
Concentration risk, percentage			22.00%

RELATED PARTY TRANSACTIONS (Details) - USD ($) $ in Millions	Apr. 29, 2019	Mar. 31, 2020	Oct. 27, 2017
Promissory Note \| Notes payable
Related Party Transaction [Line Items]
Repayment of notes payable	$ 24.7
GENBAND
Related Party Transaction [Line Items]
Promissory note issued to GENBAND equity holders			$ 22.5
GENBAND \| Minimum
Related Party Transaction [Line Items]
Promissory note interest rate		7.50%
GENBAND \| Maximum
Related Party Transaction [Line Items]
Promissory note interest rate		10.00%

LEASES - Narrative (Details) $ in Thousands	3 Months Ended		12 Months Ended
LEASES - Narrative (Details) $ in Thousands	Mar. 31, 2020 USD ($) ft²	Mar. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)
Lessee, Lease, Description [Line Items]
Additional amortization expense	$ 70	$ 0
Variable lease costs	637	$ 601	$ 900
Facilities
Lessee, Lease, Description [Line Items]
Accrual for future anticipated variable lease costs	900		900
2019 Restructuring Initiative
Lessee, Lease, Description [Line Items]
Accrual for future anticipated variable lease costs	2,465		3,101
2019 Restructuring Initiative \| Facilities
Lessee, Lease, Description [Line Items]
Additional amortization expense	100		3,700
Accrual for future anticipated variable lease costs	$ 953		$ 991
North Dallas, Texas
Lessee, Lease, Description [Line Items]
Square feet under lease \| ft²	107,800

LEASES - Assets and Liabilities (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Assets
Operating lease assets	$ 66,295	$ 36,654
Finance lease assets	2,093	2,420
Total leased assets	68,388	39,074
Current
Operating	18,201	7,719
Finance	1,376	1,005
Noncurrent
Operating	55,857	37,202
Finance	1,436	2,144
Total lease liabilities	76,870	48,070
Finance lease assets, net of accumulated depreciation	$ 2,300	$ 2,000

LEASES - Components of Lease Expense (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Leases [Abstract]
Operating lease cost	$ 3,344	$ 2,441
Finance lease cost
Amortization of leased assets	319	244
Interest on lease liabilities	55	64
Short-term lease cost	5,523	4,671
Variable lease costs (costs excluded from minimum fixed lease payments)	637	601	$ 900
Net lease cost	9,878	8,021
Accelerated rent amortization	$ 70	$ 0

LEASES - Other Information (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019	Dec. 31, 2019
Cash paid for amounts included in the measurement of lease liabilities
Operating cash flows for operating leases	$ 3,113	$ 2,355
Operating cash flows for finance leases	55	64
Financing cash flows for finance leases	$ 338	$ 230
Weighted average remaining lease term (years)
Operating leases	5 years 4 months 8 days		6 years 8 months 23 days
Finance leases	2 years 2 months 8 days		2 years 4 months 5 days
Weighted average discount rate
Operating leases	5.58%		6.50%
Finance leases	7.49%		7.54%

LEASES - Future Minimum Lease Payments (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Operating leases
Remainder of 2020	$ 16,251
Year one		$ 10,290
Year two	19,067	9,468
Year three	15,345	7,665
Year four	12,889	7,067
Year five	6,692	5,303
Year six and beyond	16,127	15,738
Total lease payments	86,371	55,531
Less: interest	(12,313)	(10,610)
Present value of lease liabilities	74,058	44,921
Finance leases
Remainder of 2020	1,214
Year one		1,644
Year two	1,179	1,159
Year three	587	581
Year four	36	0
Year five	0	0
Year six and beyond	0	0
Total lease payments	3,016	3,384
Less: interest	(204)	(235)
Present value of lease liabilities	$ 2,812	$ 3,149

COMMITMENTS AND CONTINGENCIES (Details) $ in Millions		3 Months Ended
COMMITMENTS AND CONTINGENCIES (Details) $ in Millions	Apr. 22, 2019 USD ($) case	Mar. 31, 2020 USD ($) case	Jun. 30, 2019 USD ($)
Loss Contingencies [Line Items]
Ongoing lawsuits \| case	6	6
Damages awarded from other party	$ 63.0
Cash payments from settlement			$ 37.5
Annual installment receivable	$ 25.5		25.5
Installment payments interest rate (as a percentage)	4.00%
Gain from settlement		$ 63.0
Other income (expense), net		$ 0.3
Other current assets
Loss Contingencies [Line Items]
Annual installment receivable			8.5
Other assets
Loss Contingencies [Line Items]
Annual installment receivable			$ 17.0