ADTRAN (ADTN) 10-Q 7 Aug 20 2020 Q2 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	6 Months Ended
	Jun. 30, 2020	Aug. 06, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Jun. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q2
Entity Registrant Name	ADTRAN, Inc.
Trading Symbol	ADTN
Entity Central Index Key	0000926282
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Small Business	false
Entity Emerging Growth Company	false
Entity Common Stock, Shares Outstanding		47,957,952
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	000-24612
Entity Tax Identification Number	63-0918200
Entity Address, Address Line One	901 Explorer Boulevard
Entity Address, City or Town	Huntsville
Entity Address, State or Province	AL
Entity Address, Postal Zip Code	35806-2807
City Area Code	256
Local Phone Number	963-8000
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, Par Value $0.01 per share
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Current Assets
Cash and cash equivalents	$ 69,059	$ 73,773
Restricted cash	1,186
Short-term investments	9,033	33,243
Accounts receivable, less allowance for doubtful accounts of $38 as of June 30, 2020 and December 31, 2019	95,335	90,531
Other receivables	26,026	16,566
Inventory	106,131	98,305
Prepaid expenses and other current assets	8,104	7,892
Total Current Assets	314,874	320,310
Property, plant and equipment, net	65,194	68,086
Deferred tax assets, net	7,573	7,561
Goodwill	6,968	6,968
Intangibles, net	25,455	27,821
Other assets	18,225	19,883
Long-term investments	84,383	94,489
Total Assets	522,672	545,118
Current Liabilities
Accounts payable	62,465	44,870
Bonds payable		24,600
Unearned revenue	12,090	11,963
Accrued expenses and other liabilities	12,466	13,876
Accrued wages and benefits	17,683	13,890
Income tax payable, net	2,450	3,512
Total Current Liabilities	107,154	112,711
Non-current unearned revenue	6,166	6,012
Pension liability	15,649	15,886
Deferred compensation liability	21,908	21,698
Other non-current liabilities	7,601	8,385
Total Liabilities	158,478	164,692
Commitments and contingencies (see Note 18)
Stockholders’ Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 47,957 shares outstanding as of June 30, 2020 and 79,652 shares issued and 48,020 shares outstanding as of December 31, 2019	797	797
Additional paid-in capital	278,078	274,632
Accumulated other comprehensive loss	(15,346)	(16,417)
Retained earnings	787,220	806,702
Treasury stock at cost: 31,568 and 31,636 shares at June 30, 2020 and December 31, 2019, respectively	(686,555)	(685,288)
Total Stockholders’ Equity	364,194	380,426
Total Liabilities and Stockholders’ Equity	$ 522,672	$ 545,118

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Statement Of Financial Position [Abstract]
Allowance for doubtful accounts	$ 38	$ 38
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	79,652,000	79,652,000
Common stock, shares outstanding	47,957,000	48,020,000
Treasury stock, shares	31,568,000	31,636,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income (Loss) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Sales
Total Sales	$ 128,715	$ 156,391	$ 243,238	$ 300,182
Cost of Sales
Total Cost of Sales	75,243	91,376	138,166	174,555
Gross Profit	53,472	65,015	105,072	125,627
Selling, general and administrative expenses	30,799	33,619	57,419	68,751
Research and development expenses	28,712	32,064	58,571	63,711
Gain on contingency		(1,230)		(1,230)
Asset impairments			65
Operating Income (Loss)	(6,039)	562	(10,983)	(5,605)
Interest and dividend income	331	692	687	1,283
Interest expense		(127)	(1)	(254)
Net investment gain (loss)	9,852	2,485	(1,025)	8,411
Other income (expense), net	(1,757)	(205)	(628)	650
Income (Loss) Before Income Taxes	2,387	3,407	(11,950)	4,485
Income tax (expense) benefit	(1,635)	588	2,733	280
Net Income (Loss)	$ 752	$ 3,995	$ (9,217)	$ 4,765
Weighted average shares outstanding – basic	47,958	47,802	47,957	47,792
Weighted average shares outstanding – diluted	48,254	48,036	47,957	47,939
Earnings (loss) per common share – basic	$ 0.02	$ 0.08	$ (0.19)	$ 0.10
Earnings (loss) per common share – diluted	$ 0.02	$ 0.08	$ (0.19)	$ 0.10
Network Solutions [Member]
Sales
Total Sales	$ 111,323	$ 139,167	$ 208,695	$ 264,989
Cost of Sales
Total Cost of Sales	64,071	80,175	115,697	150,909
Gross Profit	47,252	58,992	92,998	114,080
Services & Support [Member]
Sales
Total Sales	17,392	17,224	34,543	35,193
Cost of Sales
Total Cost of Sales	11,172	11,201	22,469	23,646
Gross Profit	$ 6,220	$ 6,023	$ 12,074	$ 11,547

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net Income (Loss)	$ 752	$ 3,995	$ (9,217)	$ 4,765
Other Comprehensive Income (Loss), net of tax
Net unrealized gains on available-for-sale securities	373	107	490	292
Defined benefit plan adjustments	191	150	332	271
Foreign currency translation	1,899	533	249	(627)
Other Comprehensive Income (Loss), net of tax	2,463	790	1,071	(64)
Comprehensive Income (Loss), net of tax	$ 3,215	$ 4,785	$ (8,146)	$ 4,701

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2018	$ 446,279	$ 797	$ 267,670	$ 883,975	$ (691,747)	$ (14,416)
Beginning Balance, Shares at Dec. 31, 2018		79,652
Net income (loss)	770			770
Adoption of new accounting standards	4			(381)		385
Other comprehensive income (loss), net of tax	(854)					(854)
Dividend payments ($0.09 per share)	(4,301)			(4,301)
Dividends accrued on unvested RSUs	(18)			(18)
PSUs, RSUs and restricted stock vested	(8)			(865)	857
Purchases of treasury stock	(184)				(184)
Stock-based compensation expense	1,859		1,859
Ending Balance at Mar. 31, 2019	443,547	$ 797	269,529	879,180	(691,074)	(14,885)
Ending Balance, Shares at Mar. 31, 2019		79,652
Beginning Balance at Dec. 31, 2018	446,279	$ 797	267,670	883,975	(691,747)	(14,416)
Beginning Balance, Shares at Dec. 31, 2018		79,652
Net income (loss)	4,765
Other comprehensive income (loss), net of tax	(64)
Ending Balance at Jun. 30, 2019	445,975	$ 797	270,983	878,630	(690,340)	(14,095)
Ending Balance, Shares at Jun. 30, 2019		79,652
Beginning Balance at Mar. 31, 2019	443,547	$ 797	269,529	879,180	(691,074)	(14,885)
Beginning Balance, Shares at Mar. 31, 2019		79,652
Net income (loss)	3,995			3,995
Other comprehensive income (loss), net of tax	790					790
Dividend payments ($0.09 per share)	(4,303)			(4,303)
Dividends accrued on unvested RSUs	(34)			(34)
Stock options exercised	526			(208)	734
Stock-based compensation expense	1,454		1,454
Ending Balance at Jun. 30, 2019	445,975	$ 797	270,983	878,630	(690,340)	(14,095)
Ending Balance, Shares at Jun. 30, 2019		79,652
Beginning Balance at Dec. 31, 2019	$ 380,426	$ 797	274,632	806,702	(685,288)	(16,417)
Beginning Balance, Shares at Dec. 31, 2019	79,652	79,652
Net income (loss)	$ (9,969)			(9,969)
Other comprehensive income (loss), net of tax	(1,392)					(1,392)
Dividend payments ($0.09 per share)	(4,328)			(4,328)
Dividends accrued on unvested RSUs	(32)			(32)
Deferred compensation adjustments, net of tax	(2,758)				(2,758)
PSUs, RSUs and restricted stock vested	(23)			(1,524)	1,501
Stock-based compensation expense	1,791		1,791
Ending Balance at Mar. 31, 2020	363,715	$ 797	276,423	790,849	(686,545)	(17,809)
Ending Balance, Shares at Mar. 31, 2020		79,652
Beginning Balance at Dec. 31, 2019	$ 380,426	$ 797	274,632	806,702	(685,288)	(16,417)
Beginning Balance, Shares at Dec. 31, 2019	79,652	79,652
Net income (loss)	$ (9,217)
Other comprehensive income (loss), net of tax	1,071
Ending Balance at Jun. 30, 2020	$ 364,194	$ 797	278,078	787,220	(686,555)	(15,346)
Ending Balance, Shares at Jun. 30, 2020	79,652	79,652
Beginning Balance at Mar. 31, 2020	$ 363,715	$ 797	276,423	790,849	(686,545)	(17,809)
Beginning Balance, Shares at Mar. 31, 2020		79,652
Net income (loss)	752			752
Other comprehensive income (loss), net of tax	2,463					2,463
Dividend payments ($0.09 per share)	(4,337)			(4,337)
Dividends accrued on unvested RSUs	(28)			(28)
Deferred compensation adjustments, net of tax	(24)				(24)
PSUs, RSUs and restricted stock vested	(2)			(16)	14
Stock-based compensation expense	1,655		1,655
Ending Balance at Jun. 30, 2020	$ 364,194	$ 797	$ 278,078	$ 787,220	$ (686,555)	$ (15,346)
Ending Balance, Shares at Jun. 30, 2020	79,652	79,652

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019
Statement Of Stockholders Equity [Abstract]
Dividend payments	$ 0.09	$ 0.09	$ 0.09	$ 0.09

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities:
Net income (loss)	$ (9,217)	$ 4,765
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation and amortization	8,404	8,913
Asset impairments	65
Amortization of net premium on available-for-sale investments	86	(57)
Net (gain) loss on long-term investments	1,025	(8,411)
Net loss on disposal of property, plant and equipment	52	58
Gain on contingency		(1,230)
Gain on life insurance proceeds		(1,000)
Stock-based compensation expense	3,446	3,313
Deferred income taxes	(5)	(1,880)
Changes in operating assets and liabilities:
Accounts receivable, net	(4,727)	(17,288)
Other receivables	(9,468)	11,678
Inventory	(7,878)	4,612
Prepaid expenses and other assets	1,444	4,715
Accounts payable, net	17,389	5,009
Accrued expenses and other liabilities	2,097	640
Income taxes payable	(1,032)	(2,830)
Net cash provided by operating activities	1,681	11,007
Cash flows from investing activities:
Purchases of property, plant and equipment	(3,148)	(4,307)
Proceeds from sales and maturities of available-for-sale investments	63,318	24,306
Purchases of available-for-sale investments	(31,897)	(21,544)
Acquisition of note receivable	(523)
Life insurance proceeds received		1,000
Acquisition of business		13
Net cash provided by (used in) investing activities	27,750	(532)
Cash flows from financing activities:
Proceeds from stock option exercises		526
Purchases of treasury stock		(184)
Dividend payments	(8,665)	(8,604)
Repayment of bonds payable	(24,600)
Net cash used in financing activities	(33,265)	(8,262)
Net increase (decrease) in cash, cash equivalents and restricted cash	(3,834)	2,213
Effect of exchange rate changes	306	(900)
Cash, cash equivalents and restricted cash, beginning of period	73,773	105,504
Cash, cash equivalents and restricted cash, end of period	70,245	106,817
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 198	$ 205

Summary of Significant Accounti

Summary of Significant Accounting Policies	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited condensed consolidated financial statements of ADTRAN ® In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 25, 2020. Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. The more significant estimates include excess and obsolete inventory reserves, warranty reserves, customer rebates, determination and accrual of deferred revenue components of multi-element sales agreements, estimated costs to complete obligations associated with deferred and accrued revenues and network installations, estimated income tax provision and income tax contingencies, fair value of stock-based compensation, assessment of goodwill and other intangibles for impairment, estimated lives of intangible assets, estimated pension liability and fair value of investments. Actual amounts could differ significantly from these estimates. We assessed certain accounting matters that generally require consideration of forecasted financial information in context with the information reasonably available to us and the unknown future impacts of the novel coronavirus (“COVID-19”) as of June 30, 2020 and through the date of this report. The accounting matters assessed included, but were not limited to, the allowance for doubtful accounts, current estimated credit losses, stock-based compensation, carrying value of goodwill, intangibles and other long-lived assets, financial assets, valuation allowances for tax assets and revenue recognition. While there was not a material impact to our consolidated financial statements as of and for the quarter ended June 30, 2020 resulting from these assessments, future conditions related to the magnitude and duration of the COVID-19 pandemic, as well as other factors, could result in material impacts to our consolidated financial statements in future reporting periods. Correction of Immaterial Misstatements During the three months ended June 30, 2019, the Company determined that there was an immaterial misstatement of its excess and obsolete inventory reserves in its previously issued annual and interim financial statements. The Company corrected this misstatement by recognizing a $0.8 million out-of-period adjustment during the three months ended June 30, 2019, which increased its excess and obsolete inventory reserve and cost of goods sold for the period. For the six months ended June 30, 2019, the out-of-period adjustment was a cumulative $0.2 million reduction in its excess and obsolete inventory reserve and cost of goods sold. In addition, the Company determined that a cash inflow related to an insurance recovery was incorrectly classified as a cash flow from operations instead of a cash flow from investing activities within the unaudited Condensed Consolidated Statement of Cash Flows for the three months ended March 31, 2019. The Company corrected this misstatement in the Unaudited Condensed Consolidated Statement of Cash Flows for the six months ended June 30, 2019 to correctly reflect the $1.0 million insurance recovery as a cash inflow from investing activities. During the first quarter of 2020, it was determined that certain investments held in the Company’s stock for a deferred compensation plan accounted for as a Rabbi trust were incorrectly classified as long-term investments with the fair value of such investments incorrectly marked to market at each period end rather than classified as treasury stock held at historical cost. This plan has been in existence since 2011. The Company corrected this misstatement as an out-of-period adjustment in the three months ended March 31, 2020 by remeasuring the investment assets to their historical cost basis through the recording of a net investment gain of $1.5 million in the unaudited Condensed Consolidated Statement of Income (Loss) and then correcting the classification by decreasing the long-term investment balance at its remeasured cost basis of $2.8 million to treasury stock in the unaudited Condensed Consolidated Balance Sheet as of March 31, 2020. Management has determined that this misstatement was not material to any of its previously issued financial statements and that correction of the misstatement is also not expected to be material to the 2020 annual financial results on either a quantitative or qualitative basis. Recently Adopted Accounting Pronouncements During 2020, we adopted the following accounting standards, which had the following impacts on our consolidated financial statements: In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Codification Improvements to Topic 326 Financial Instruments – Credit Losses, Codification Improvements to Topic 326, Financial Instruments–Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, Financial Instruments – Credit Losses (Topic 326): Targeted Transition Relief, Codification Improvements to Topic 326, Financial Instruments – Credit Losses elected to carry forward legacy disclosures for comparative periods and did not adjust the comparative period financial information. Additionally, the Company made an accounting policy election, at the class of financing receivable, not to measure the allowance for credit losses for accrued interest receivables, as the Company writes off the uncollectable accrued interest receivable by reversing any previously recorded interest income in a timely manner (as soon as these amounts are determined to be uncollectable). The adoption of this standard did not have a material effect on our consolidated financial statements. See Note 19 for additional information. In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment 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, Fair Value Measurement. Concepts Statement No. 8 — Conceptual Framework for Financial Reporting — Chapter 8 — Notes to Financial Statements 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 clarifies certain aspects of ASU 2015-05, Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement. Specifically, ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementations costs incurred to develop or obtain internal use software. The Company adopted ASU 2018-15 on January 1, 2020, retrospectively. The adoption of this standard resulted in a reclass ification of $ 5.6 million from property, plant and equipment to other assets for certain previously capitalized costs related to information technology implementation projects that had not yet been placed in service on the C ondensed C onsolidated B alance S heet s as of June 30 , 2020 and December 31, 2019 . There was no impact to previously reported net cash provided by (used in) operations on the statement of cash flows and no impact to the statements of income (loss) as no portion of the capitalized asset was depreciated in prior periods. The following table illustrates the impact of adoption of ASU 2018-15 on the Condensed Consolidated Balance Sheet as of December 31, 2019: As of December 31, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Balance Sheet Property, plant and equipment, net $ 73,708 $ (5,622 ) $ 68,086 Other assets $ 14,261 $ 5,622 $ 19,883 The following table illustrates the impact of adoption of ASU 2018-15 on the Condensed Consolidated Statement of Income for the three and six months ended June 30, 2019 and the Condensed Consolidated Statement of Cash Flows for six months ended June 30, 2019: Three months ended June 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Income (Loss) Net income $ 3,995 $ — $ 3,995 Six months ended June 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Income (Loss) Net income $ 4,765 $ — $ 4,765 Condensed Consolidated Statement of Cash Flows Net cash provided by operating activities $ 11,007 $ — $ 11,007 In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes, Recent Accounting Pronouncements Not Yet Adopted In August 2018, the FASB ASU Compensation – Retirement Benefits – Defined Benefit Plans – General (Subtopic 715-20): Disclosure Framework – Changes to the Disclosure Requirements for Defined Benefit Plans,

Cash ,Cash Equivalents and Rest

Cash ,Cash Equivalents and Restricted Cash	6 Months Ended
	Jun. 30, 2020
Cash And Cash Equivalents [Abstract]
Cash ,Cash Equivalents and Restricted Cash	2. CASH, CASH EQUIVALENTS AND RESTRICTED CASH The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the consolidated statement of cash flows: (In thousands) June 30, 2020 Cash and cash equivalents $ 69,059 Restricted cash 1,186 Cash, cash equivalents and restricted cash $ 70,245 The Company did not have any restricted cash as of June 30, 2019. See Note 18 for additional information regarding restricted cash.

Revenue

Revenue	6 Months Ended
	Jun. 30, 2020
Revenue From Contract With Customer [Abstract]
Revenue	3. REVENUE The following is a description of the principal activities from which revenue is generated by reportable segment: Network Solutions Segment - Includes hardware products and software-defined next-generation virtualized solutions used in service provider or business networks, as well as prior generation products. Services & Support Segment - Includes maintenance, network implementation, solutions integration and managed services, which include hosted cloud services and subscription services. Sales by Category In addition to our reportable segments, revenue is also reported for the following three categories – Access & Aggregation, Subscriber Solutions & Experience and Traditional & Other Products. The following tables disaggregate revenue by reportable segment and revenue category for the three and six months ended June 30, 2020 and 2019: Three Months Ended June 30, 2020 June 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 69,721 $ 13,055 $ 82,776 $ 96,262 $ 13,159 $ 109,421 Subscriber Solutions & Experience 38,081 2,312 40,393 38,444 2,058 40,502 Traditional & Other Products 3,521 2,025 5,546 4,461 2,007 6,468 Total $ 111,323 $ 17,392 $ 128,715 $ 139,167 $ 17,224 $ 156,391 Six Months Ended June 30, 2020 June 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 122,776 $ 25,966 $ 148,742 $ 181,935 $ 27,264 $ 209,199 Subscriber Solutions & Experience 78,064 4,508 82,572 73,163 4,092 77,255 Traditional & Other Products 7,855 4,069 11,924 9,891 3,837 13,728 Total $ 208,695 $ 34,543 $ 243,238 $ 264,989 $ 35,193 $ 300,182 Revenue allocated to remaining performance obligations represents contract revenues that have not yet been recognized for contracts with a duration of greater than one year. As of June 30, 2020, we did not have any significant performance obligations related to customer contracts that had an original expected duration of one year or more, other than maintenance services, which are satisfied over time. As a practical expedient, for certain contracts we recognize revenue equal to the amounts that we are entitled to invoice, which correspond to the value of completed performance obligations to date. The amount related to these performance obligations was $16.0 million and $13.6 million as of June 30, 2020 and December 31, 2019, respectively. The Company expects to recognize 62% of the $16.0 million as of June 30, 2020 over the next 12 months, with the remainder to be recognized thereafter. The following table provides information about receivables, contract assets and unearned revenue from contracts with customers: (In thousands) June 30, 2020 December 31, 2019 Accounts receivable, net $ 95,335 $ 90,531 Contract assets (1) $ 1,028 $ 2,812 Unearned revenue $ 12,090 $ 11,963 Non-current unearned revenue $ 6,166 $ 6,012 (1) Included in other receivables on the Condensed Consolidated Balance Sheets. Of the outstanding unearned revenue balances as of December 31, 2019 and December 31, 2018, $2.4 million and $3.6 million were recognized as revenue during the three months ended June 30, 2020 and 2019, respectively, and $8.1 million and $10.5 million were recognized as revenue during the six months ended June 30, 2020 and 2019, respectively.

Income Taxes

Income Taxes	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	4. INCOME TAXES Our effective tax rate increased from a benefit of 17.3% for the three months ended June 30, 2019 to an expense of 68.5% for the three months ended June 30, 2020 and decreased from a benefit of 6.2% for the six months ended June 30, 2019 to a benefit of 22.9% for the six months ended June 30, 2020. The change in the effective tax rate for the three months ended June 30, 2020 was impacted by tax expense in our international operations and additional changes in the valuation allowance related to our domestic operations. The change in the effective tax rate for the three and six months ended June 30, 2019 was primarily driven by the shift to profitability for the three and six months ended June 30, 2019, with tax expense being offset by a 29.1% rate reduction related to a transfer pricing study completed during the second quarter of 2019 that resulted in the assignment of operating expenditures to specific Company locations, and the effective income tax rates among the respective jurisdictions. The decrease in the effective tax rate for the six months ended June 30, 2020 was primarily driven by a tax benefit of $7.4 million recognized during the six months ended June 30, 2020 as a result of the Coronavirus Aid, Relief, and Economic Security Act (the “CARES Act”) signed into law on March 27, 2020, which allowed for the carryback of federal net operating losses, partially offset with tax expense in our international operations and changes in our valuation allowance related to our domestic operations. An increase in the valuation allowance against our domestic deferred tax assets was recorded in the amount of $3.6 million during the three and six months ended June 30, 2020. The Company continually reviews the adequacy of its valuation allowance and recognizes the benefits of deferred tax assets only as the reassessment indicates that it is more likely than not that the deferred tax assets will be recognized in accordance with ASC 740, Income Taxes. Supplemental balance sheet information related to deferred tax assets as of June 30, 2020 and December 31, 2019 is as follows: June 30, 2020 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 50,164 $ (50,164 ) $ — International 9,603 (2,030 ) 7,573 Total $ 59,767 $ (52,194 ) $ 7,573 December 31, 2019 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 46,266 $ (46,266 ) $ — International 9,911 (2,350 ) 7,561 Total $ 56,177 $ (48,616 ) $ 7,561

Pension Benefit Plan

Pension Benefit Plan	6 Months Ended
	Jun. 30, 2020
Compensation And Retirement Disclosure [Abstract]
Pension Benefit Plan	5. PENSION BENEFIT PLAN The following table summarizes the components of net periodic pension cost related to a defined benefit pension plan covering employees in certain foreign countries for the three and six months ended June 30, 2020 and 2019: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Service cost $ 307 $ 368 $ 617 $ 743 Interest cost 108 159 216 321 Expected return on plan assets (407 ) (348 ) (817 ) (703 ) Amortization of actuarial losses 235 199 472 402 Net periodic pension cost $ 243 $ 378 $ 488 $ 763 The components of net periodic pension cost, other than the service cost component, are included in other income (expense), net in the Condensed Consolidated Statements of Income (Loss). Service cost is included in cost of sales, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of Income (Loss).

Stock-Based Compensation

Stock-Based Compensation	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation	6. STOCK-BASED COMPENSATION The following table summarizes stock-based compensation expense related to stock options, performance stock units (“PSUs”), restricted stock units (“RSUs”) and restricted stock for the three and six months ended June 30, 2020 and 2019: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Stock-based compensation expense included in cost of sales $ 87 $ 85 $ 202 $ 189 Selling, general and administrative expense 971 662 2,046 1,725 Research and development expense 597 707 1,198 1,399 Stock-based compensation expense included in operating expenses 1,568 1,369 3,244 3,124 Total stock-based compensation expense 1,655 1,454 3,446 3,313 Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock (394 ) (332 ) (821 ) (775 ) Total stock-based compensation expense, net of tax $ 1,261 $ 1,122 $ 2,625 $ 2,538 PSUs, RSUs and Restricted S tock The following table summarizes PSUs, RSUs and restricted stock outstanding as of December 31, 2019 and June 30, 2020 and the changes that occurred during the six months ended June 30, 2020. Number of Shares (in thousands) Weighted Avg. Grant Date Fair Value (per share) Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2019 1,891 $ 14.58 PSUs, RSUs and restricted stock granted 399 $ 8.21 PSUs, RSUs and restricted stock vested (13 ) $ 12.32 PSUs, RSUs and restricted stock forfeited (518 ) $ 19.27 Unvested PSUs, RSUs and restricted stock outstanding, June 30, 2020 1,759 $ 11.78 During the six months ended June 30, 2020, the Company issued 0.3 million performance-based PSUs under the ADTRAN, Inc. 2015 Employee Stock Incentive Plan (the “2015 Employee Plan”) to its executive officers and certain employees. The grant-date fair value of these performance-based awards is based on the closing price of the Company’s stock on the date of grant. Subject to the grantee’s continued employment, the grantee has the ability to earn shares in a range of 0% to 142.8% of the awarded number of PSUs based on the achievement of defined performance target at the end of a three-year The fair value of RSUs and restricted stock is equal to the closing price of our stock on the date of grant. The fair value of PSUs with market conditions is calculated using a Monte Carlo simulation valuation method. As of June 30, 2020, total unrecognized compensation expense related to non-vested market-based PSUs, RSUs and restricted stock was approximately $12.7 million, which will be recognized over the remaining weighted-average period of 2.5 years. Unrecognized compensation expense will be adjusted for actual forfeitures. Under the 2020 Employee Plan, the Company is authorized to issue 2.8 million shares of common stock to certain employees, key service providers and advisors through incentive stock options and non-qualified stock options, stock appreciation rights, RSUs and restricted stock, any of which may be subject to performance-based conditions. Options, RSUs and restricted stock granted under the 2020 Employee Plan reduce the shares authorized for issuance under the 2020 Employee Plan by one (1) share of common stock for each share underlying the award. Forfeitures, cancellations or expirations of awards granted under the 2015 Employee Plan increase the shares authorized for issuance under the 2020 Employee Plan, with forfeitures, cancellations or expirations of RSUs and restricted stock increasing the shares authorized for issuance by 2.5 shares of common stock for each share underlying the award. Forfeitures cancellations or expirations of options from the 2015 Employee Plan increase the shares authorized for issuance under the 2020 Employee Plan by one (1) share of common stock for each share underlying the award. RSUs and restricted stock granted under the 2020 Employee Plan will typically vest pursuant to a four-year four-year ten-year Under the 2020 Directors Plan, the Company is authorized to issue 0.4 million shares of common stock. Under the 2020 Directors Plan, the Company may issue stock options, restricted stock and RSUs to our non-employee directors. Stock awards issued under the 2020 Directors Plan typically will become vested in full on the first anniversary of the grant date. Options issued under the 2020 Directors Plan will have a ten-year As of June 30, 2020, 3.4 million shares were available for issuance under stockholder-approved equity plans. Stock Options The following table summarizes stock options outstanding as of December 31, 2019 and June 30, 2020 and the changes that occurred during the six months ended June 30, 2020: Number of Stock Options (in thousands) Weighted Avg. Exercise Price (per share) Weighted Avg. Remaining Contractual Life (in years) Aggregate Intrinsic Value (in thousands) Stock options outstanding, December 31, 2019 3,572 $ 22.88 3.4 $ — Stock options exercised — $ — Stock options forfeited — $ — Stock options expired (265 ) $ 21.20 Stock options outstanding, June 30, 2020 3,307 $ 22.93 2.9 $ — Stock options exercisable, June 30, 2020 3,305 $ 22.93 2.9 $ — As of June 30, 2020, total unrecognized compensation expense related to non-vested stock options was approximately $4 thousand, which will be recognized over the remaining weighted-average period of 0.3 years. Unrecognized compensation expense will be adjusted for actual forfeitures. There were no stock options granted during the three and six months ended June 30, 2020 and 2019. All of the options were previously issued at exercise prices that approximated fair market value at the date of grant. The aggregate intrinsic value of stock options represents the total pre-tax intrinsic value (the difference between ADTRAN’s closing stock price on the last trading day of the quarter and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on June 30, 2020. The amount of aggregate intrinsic value will change based on the fair market value of ADTRAN’s stock and was zero as of June 30, 2020. The total pre-tax intrinsic value of options exercised during the six months ended June 30, 2020 was zero.

Investments

Investments	6 Months Ended
	Jun. 30, 2020
Investments Debt And Equity Securities [Abstract]
Investments	7. INVESTMENTS Debt Securities and Other Investments As of June 30, 2020, the following debt securities and other investments were included on the Condensed Consolidated Balance Sheet and recorded at fair value: Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 13,747 $ 168 $ (1 ) $ 13,914 Municipal fixed-rate bonds 2,379 21 — 2,400 Asset-backed bonds 7,600 86 (4 ) 7,682 Mortgage/Agency-backed bonds 7,944 152 (12 ) 8,084 U.S. government bonds 7,935 211 — 8,146 Foreign government bonds 540 — — 540 Commercial paper 1,120 4 — 1,124 Variable-rate demand notes 300 — — 300 Other 442 — — 442 Available-for-sale debt securities held at fair value $ 42,007 $ 642 $ (17 ) $ 42,632 A s of December 31, 2019 , the following debt securities and other investments were included on the Condensed Consolidated Balance sheet and recorded at fair value: Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 9,304 $ 80 $ — $ 9,384 Municipal fixed-rate bonds 930 — — 930 Asset-backed bonds 6,867 26 (3 ) 6,890 Mortgage/Agency-backed bonds 6,944 26 (8 ) 6,962 U.S. government bonds 12,311 21 (9 ) 12,323 Foreign government bonds 372 — (1 ) 371 Variable-rate demand notes 800 — — 800 Available-for-sale debt securities held at fair value $ 37,528 $ 153 $ (21 ) $ 37,660 As of June 30, 2020, contractual maturities related to debt securities and other investments were as follows: (In thousands) Corporate bonds Municipal fixed-rate bonds Asset- backed bonds Mortgage/ Agency- backed bonds U.S. government bonds Foreign government bonds Commercial paper Variable-rate demand notes Other Less than one year $ 5,441 $ 738 $ 465 $ 146 $ — $ — $ 1,124 $ — $ 442 One to two years 2,926 528 465 603 1,638 75 — — — Two to three years 5,547 757 1,141 1,528 6,065 465 — — — Three to five years — 377 3,932 — 443 — — — — Five to ten years — — 982 1,890 — — — — — More than ten years — — 697 3,917 — — — 300 — Total $ 13,914 $ 2,400 $ 7,682 $ 8,084 $ 8,146 $ 540 $ 1,124 $ 300 $ 442 Actual maturities may differ from contractual maturities as some borrowers have the right to call or prepay obligations with or without call or prepayment penalties. Realized gains and losses on sales of debt securities are computed under the specific identification method. The following table presents gross realized gains and losses related to our debt securities: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Gross realized gains on debt securities $ 190 $ 8 $ 233 $ 49 Gross realized losses on debt securities (19 ) (14 ) (39 ) (33 ) Total gain recognized, net $ 171 $ (6 ) $ 194 $ 16 The Company’s investment policy provides limitations for issuer concentration, which limits, at the time of purchase, the concentration in any one issuer to 5% of the market value of our total investment portfolio. The Company did not purchase any available-for-sale debt security with credit deterioration during the three months ended June 30, 2020. Marketable Equity Securities Our marketable equity securities consist of publicly traded stock, funds and certain other investments measured at fair value or cost (where appropriate). During the three months ended March 31, 2019, an outstanding note receivable of $4.3 million was repaid and reissued in the form of debt and equity. Of the outstanding $4.3 million, $3.4 million was issued as an equity investment, which represented a non-cash investing activity. We elected to record this equity investment that does not have a readily determinable fair value using the measurement alternative. Under the measurement alternative, equity investments that do not have a readily determinable fair value can be recorded at cost less impairment, if any, adjusted for observable price changes for an identical or similar investment. The carrying value of this investment under the measurement alternative was $3.4 million as of December 31, 2019. During the six months ended June 30, 2020, an impairment charge of $1.6 million was recorded related to this equity investment, which is included in net investment gain (loss) on the Condensed Consolidated Statement of Income (Loss). As a result, the carrying value of this investment was $1.8 million as of June 30, 2020. The remaining amount, $0.9 million of the original $4.3 million note receivable, was reissued as a new note receivable, which is included in long-term investments on the Condensed Consolidated Balance Sheets as of June 30, 2020 and December 31, 2019, and represented a non-cash investing activity during the six months ended June 30, 2019. No impairment charge was recognized related to the note receivable as it is a secured loan. Realized and unrealized gains and losses related to marketable equity securities for the three and six months ended June 30, 2020 and 2019 were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Realized gains (losses) on equity securities sold $ 328 $ (49 ) $ (2,108 ) $ (63 ) Unrealized gains (losses) on equity securities held 9,353 2,540 889 8,458 Total gain (loss) recognized, net $ 9,681 $ 2,491 $ (1,219 ) $ 8,395 U.S. GAAP establishes a three-level valuation hierarchy based upon observable and unobservable inputs for fair value measurement of financial instruments: • Level 2 – Significant inputs that are observable; values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; • Level 3 – Significant unobservable inputs; values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs could include information supplied by investees. The Company’s cash equivalents and investments held at fair value are categorized into this hierarchy as follows: Fair Value Measurements as of June 30, 2020 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,697 $ 1,697 $ — $ — U.S. government securities 1,250 1,250 — — Commercial paper 100 — 100 — Available-for-sale debt securities Corporate bonds 13,914 — 13,914 — Municipal fixed-rate bonds 2,400 — 2,400 — Asset-backed bonds 7,682 — 7,682 — Mortgage/Agency-backed bonds 8,084 — 8,084 — U.S. government bonds 8,146 8,146 — — Foreign government securities 540 — 540 — Commercial paper 1,124 — 1,124 — Variable-rate demand notes 300 — 300 — Other 442 — — 442 Marketable equity securities Marketable equity securities – various industries 26,116 26,116 — — Deferred compensation plan assets 20,468 20,468 — — Other investments 1,223 1,223 — — Total $ 93,486 $ 58,900 $ 34,144 $ 442 Fair Value Measurements as of December 31, 2019 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,309 $ 1,309 $ — $ — Available-for-sale debt securities Corporate bonds 9,384 — 9,384 — Municipal fixed-rate bonds 930 — 930 — Asset-backed bonds 6,890 — 6,890 — Mortgage/Agency-backed bonds 6,962 — 6,962 — U.S. government bonds 12,323 12,323 — — Foreign government bonds 371 — 371 — Variable-rate demand notes 800 — 800 — Marketable equity securities Marketable equity securities – various industries 35,501 35,501 — — Equity in escrow 298 298 — — Deferred compensation plan assets 21,698 21,698 — — Other investments 2,442 2,442 — — Total $ 98,908 $ 73,571 $ 25,337 $ — The fair value of our Level 2 securities is calculated using a weighted average market price for each security. Market prices are obtained from a variety of industry standard data providers, large financial institutions and other third-party sources. These multiple market prices are used as inputs into a distribution-curve-based algorithm to determine the daily market value of each security. The fair value of Level 3 securities is calculated based on unobservable inputs. Quantitative information with respect to unobservable inputs consists of third-party valuations performed in accordance with ASC 820 – Fair Value Measurement.

Inventory

Inventory	6 Months Ended
	Jun. 30, 2020
Inventory Disclosure [Abstract]
Inventory	8. INVENTORY As of June 30, 2020 and December 31, 2019, inventory consisted of the following: June 30, December 31, (In thousands) 2020 2019 Raw materials $ 37,057 $ 36,987 Work in process 610 1,085 Finished goods 68,464 60,233 Total inventory $ 106,131 $ 98,305 Inventory reserves are established for estimated excess and obsolete inventory equal to the difference between the cost of the inventory and the estimated net realizable value of the inventory based on estimated reserve percentages, which consider historical usage, known trends, inventory age and market conditions. As of June 30, 2020 and December 31, 2019, inventory reserves were $35.9 million and $34.1 million, respectively

Property, Plant and Equipment

Property, Plant and Equipment	6 Months Ended
	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	9. PROPERTY, PLANT AND EQUIPMENT At June 30, 2020 and December 31, 2019, property, plant and equipment consisted of the following: June 30, December 31, (In thousands) 2020 2019 Land $ 4,575 $ 4,575 Building and land improvements 34,897 34,797 Building 68,155 68,157 Furniture and fixtures 19,972 19,959 Computer hardware and software 69,564 68,777 Engineering and other equipment 131,785 130,430 Total property, plant and equipment 328,948 326,695 Less: accumulated depreciation (263,754 ) (258,609 ) Total property, plant and equipment, net $ 65,194 $ 68,086 Long-lived assets used in operations are reviewed for impairment whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable and the undiscounted cash flows estimated to be generated by the asset are less than the asset’s carrying value. Due to the current economic environment, particularly related to COVID-19, the Company assessed impairment triggers related to long-lived assets during the second quarter of 2020. Based on this assessment, no triggers occurred to perform an impairment test, and no impairment losses of long-lived assets were recorded Depreciation expense was $3.0 million and $3.1 million for the three months ended June 30, 2020 and 2019, respectively, and $6.0 million and $6.2 million for the six months ended June 30, 2020 and 2019, respectively, which is recorded in cost of sales, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of Income (Loss).

Goodwill

Goodwill	6 Months Ended
	Jun. 30, 2020
Goodwill Disclosure [Abstract]
Goodwill	10. GOODWILL Goodwill was $7.0 million as of June 30, 2020 and December 31, 2019, of which $6.6 million and $0.4 million was allocated to our Network Solutions and Services & Support reportable segments, respectively. The Company evaluates the carrying value of goodwill during the fourth quarter of each year and between annual evaluations if events occur or circumstances change that could more likely than not reduce the fair value of the reporting unit below its carrying amount. We assess qualitative factors to determine whether the fair value of the reporting unit to which the goodwill is assigned is less than its carrying amount and recognize an impairment charge for the amount by which the carrying value exceeds the fair value of the reporting unit. Due to the current economic environment, particularly related to COVID-19, the Company performed a triggering event assessment, in which no triggers were identified. Therefore, no interim impairment test of goodwill was performed as of June 30, 2020, and no impairment of goodwill was recorded.

Intangible Assets

Intangible Assets	6 Months Ended
	Jun. 30, 2020
Intangible Assets Net Excluding Goodwill [Abstract]
Intangible Assets	11. Intangible assets as of June 30, 2020 and December 31, 2019 consisted of the following: June 30, 2020 December 31, 2019 (In thousands) Gross Carrying Amount Accumulated Amortization Net Book Value Gross Carrying Amount Accumulated Amortization Net Book Value Customer relationships $ 20,742 $ (6,690 ) $ 14,052 $ 22,356 $ (7,233 ) $ 15,123 Developed technology 8,200 (1,977 ) 6,223 10,170 (3,379 ) 6,791 Licensed technology 5,900 (1,503 ) 4,397 5,900 (1,174 ) 4,726 Supplier relationships 2,800 (2,800 ) — 2,800 (2,508 ) 292 Licensing agreements 560 (116 ) 444 560 (79 ) 481 Patents 500 (260 ) 240 500 (226 ) 274 Trade names 210 (111 ) 99 310 (176 ) 134 Total $ 38,912 $ (13,457 ) $ 25,455 $ 42,596 $ (14,775 ) $ 27,821 The Company evaluates the carrying value of intangible assets whenever events or changes in circumstances indicate that the carrying amount of an asset may not be recoverable and the undiscounted cash flows estimated to be generated by the asset are less than the asset’s carrying value. Due to the current economic environment, particularly related to COVID-19, the Company assessed impairment triggers related to intangible assets during the second quarter of 2020. Based on this assessment, no triggers occurred to perform an impairment test, and no impairment losses of intangible assets were recorded. Amortization expense was $1.0 million and $1.3 million for the three months ended June 30, 2020 and 2019, respectively, and $2.4 million and $2.7 million for the six months ended June 30, 2020 and 2019, respectively, and was included in cost of sales, selling, general and administrative expenses and research and development expenses As of June 30, 2020, estimated future amortization expense of intangible assets was as follows: (In thousands) 2020 $ 2,076 2021 4,095 2022 3,472 2023 3,320 2024 3,227 Thereafter 9,265 Total $ 25,455

Leases

Leases	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Leases	12. LEASES Operating Leases Operating leases consist of office space, automobiles and various other equipment in the U.S. and in certain international locations in which we do business. Other contracts, such as manufacturing agreements and service agreements, are reviewed to determine if they contain any embedded leases. As of June 30, 2020, the operating leases had remaining lease terms of one month to five years, some of which include options to extend the leases for up to nine years, and some of which include options to terminate the leases within three months (In thousands) Classification June 30, 2020 December 31, 2019 Assets Operating lease asset Other assets $ 5,973 $ 8,452 Total lease asset $ 5,973 $ 8,452 Liabilities Current operating lease liability Accrued expenses $ 1,854 $ 2,676 Non-current operating lease liability Other non-current liabilities 4,134 5,818 Total lease liability $ 5,988 $ 8,494 Lease expense related to short-term leases (initial term of less than 12 months) was $5 thousand and $0.1 million for the three months ended June 30, 2020 and 2019, respectively, and was $14 thousand and $0.3 million for the six months ended June 30, 2020 and 2019, respectively, and was included in cost of sales, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of Income (Loss). Lease expense related to variable lease payments that do not depend on an index or rate, such as real estate taxes and insurance reimbursements, was $0.1 million and $0.3 million for the three months ended June 30, 2020 and 2019, respectively and was $0.3 million and $0.4 million for the six months ended June 30, 2020 and 2019, respectively. Components of lease expense included in the Condensed Consolidated Statements of Income (Loss) for the three and six months ended June 30, 2020 and 2019 were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Selling, general and administrative expenses $ 271 $ 349 $ 598 $ 698 Research and development expenses 251 430 676 884 Cost of sales 26 17 47 33 Total operating lease expense $ 548 $ 796 $ 1,321 $ 1,615 As of June 30, 2020 and December 31, 2019, operating lease liabilities included on the Condensed Consolidated Balance Sheets by future maturity were as follows: (In thousands) June 30, 2020 December 31, 2019 2020 $ 1,048 $ 2,856 2021 1,815 2,412 2022 1,514 1,705 2023 1,110 1,160 2024 478 482 Thereafter 264 264 Total lease payments 6,229 8,879 Less: Interest (241 ) (385 ) Present value of lease liabilities $ 5,988 $ 8,494 Future o perating lease payments include $0.5 million related to options to extend lease terms that are reasonably certain of being exercised. There are no legally binding leases that have not yet commenced A n incremental borrowing rate is used based on information available at the commencement date in determining the present value of lease payments. The incremental borrowing rate was determined on a portfolio basis by grouping leases with similar terms as well as grouping leases based on a U.S. dollar or Euro functional currency. The actual rate is then determined based on a credit spread over LIBOR as well as the Bloomberg Curve Matrix for the U . S . Communications section. The following table provides information about the weighted average lease terms and weighted average discount rates as of June 30, 2020 : As of June 30, 2020 Weighted average remaining lease term (in years) Operating leases with USD functional currency 2.5 Operating leases with Euro functional currency 4.0 Weighted average discount rate Operating leases with USD functional currency 4.46 % Operating leases with Euro functional currency 1.83 % Supplemental cash flow information related to operating leases is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Cash paid for amounts included in the measurement of operating lease assets / liabilities Cash used in operating activities related to operating leases $ 770 $ 797 $ 1,477 $ 1,608 Right-of-use assets obtained in exchange for lease obligations $ 8 $ 9 $ 93 $ 10,396 Net Investment in Sales-Type Leases We are the lessor in sales-type lease arrangements for network equipment, which have initial terms of up to five years, and consisted of the following as of June 30, 2020 and December 31, 2019: (In thousands) June 30, 2020 December 31, 2019 Current minimum lease payments receivable (1) $ 923 $ 1,201 Non-current minimum lease payments receivable (2) 566 889 Total minimum lease payments receivable 1,489 2,090 Less: Current unearned revenue 265 365 Less: Non-current unearned revenue 92 163 Net investment in sales-type leases $ 1,132 $ 1,562 (1) Included in other receivables on the Condensed Consolidated Balance Sheets. (2) Included in other assets on the Condensed Consolidated Balance Sheets. C omponents of gross profit related to sales-type leases recognized at the lease commencement date and interest and dividend income included in the Condensed Consolidated Statements of Income (Loss) for the three and six months ended June 30, 2020 and 2019 were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Sales - Network Solutions $ 12 $ 109 $ 50 $ 1,621 Less: Cost of sales - Network Solutions 4 44 20 635 Gross profit $ 8 $ 65 $ 30 $ 986 Interest and dividend income $ 11 $ 99 $ 24 $ 186

Alabama State Industrial Develo

Alabama State Industrial Development Authority Financing and Economic Incentives	6 Months Ended
	Jun. 30, 2020
Text Block [Abstract]
Alabama State Industrial Development Authority Financing and Economic Incentives	13. ALABAMA STATE INDUSTRIAL DEVELOPMENT AUTHORITY FINANCING AND ECONOMIC INCENTIVES This certificate of deposit, which totaled $25.6 million, was included in short-term investments on the Condensed Consolidated Balance Sheet as of December 31, 2019.

Stockholders' Equity

Stockholders' Equity	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Stockholders' Equity	14. STOCKHOLDERS’ EQUITY Stock Repurchase Program Since 1997, the Company’s Board of Directors has approved multiple share repurchase programs that have authorized repurchases of its common stock, which are implemented through open market or private purchases from time to time as conditions warrant. During the six months ended June 30, 2020, we did not repurchase shares of our common stock. As of June 30, 2020, we had the authority to purchase an additional 2.5 million shares of our common stock under the current authorization of up to 5.0 million shares. Accumulated Other Comprehensive Income (Loss) The following tables present the changes in accumulated other comprehensive loss, net of tax, by component for the three months ended June 30, 2020 and 2019: Three Months Ended June 30, 2020 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (1) Total As of March 31, 2020 $ (167 ) $ (9,085 ) $ (8,942 ) $ 385 $ (17,809 ) Other comprehensive income before reclassifications 881 — 1,899 — 2,780 Amounts reclassified from accumulated other comprehensive income (loss) (508 ) 191 — — (317 ) Net current period other comprehensive income 373 191 1,899 — 2,463 As of June 30, 2020 $ 206 $ (8,894 ) $ (7,043 ) $ 385 $ (15,346 ) Three Months Ended June 30, 2019 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (1) Total As of March 31, 2019 $ (378 ) $ (7,920 ) $ (6,972 ) $ 385 $ (14,885 ) Other comprehensive income before reclassifications 180 — 533 — 713 Amounts reclassified from accumulated other comprehensive income (loss) (73 ) 150 — — 77 Net current period other comprehensive income 107 150 533 — 790 As of June 30, 2019 $ (271 ) $ (7,770 ) $ (6,439 ) $ 385 $ (14,095 ) (1) The following tables present the changes in accumulated other comprehensive loss, net of tax , by component for the six months ended June 30, 2020 and 2019 : Six Months Ended June 30, 2020 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (1) Total As of December 31, 2019 $ (284 ) $ (9,226 ) $ (7,292 ) $ 385 $ (16,417 ) Other comprehensive income (loss) before reclassifications (50 ) — 249 — 199 Amounts reclassified from accumulated other comprehensive income 540 332 — — 872 Net current period other comprehensive income 490 332 249 — 1,071 As of June 30, 2020 $ 206 $ (8,894 ) $ (7,043 ) $ 385 $ (15,346 ) Six Months Ended June 30, 2019 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (1) Total As of December 31, 2018 $ (563 ) $ (8,041 ) $ (5,812 ) $ — $ (14,416 ) Other comprehensive income (loss) before reclassifications 411 — (627 ) — (216 ) Amounts reclassified from accumulated other comprehensive income (loss) (119 ) 271 — — 152 Amounts reclassified to retained earnings (1) — — — 385 385 Net current period other comprehensive income (loss) 292 271 (627 ) 385 321 As of June 30, 2019 $ (271 ) $ (7,770 ) $ (6,439 ) $ 385 $ (14,095 ) (1) The following tables present the details of reclassifications out of accumulated other comprehensive loss for the three months ended June 30, 2020 and 2019: Three Months Ended June 30, 2020 (In thousands) Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gains on sales of securities $ 686 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (277 ) (1) Total reclassifications for the period, before tax 409 Tax expense (92 ) Total reclassifications for the period, net of tax $ 317 (1) Three Months Ended June 30, 2019 (In thousands) Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gains on sales of securities $ 99 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (217 ) (1) Total reclassifications for the period, before tax (118 ) Tax benefit 41 Total reclassifications for the period, net of tax $ (77 ) (1) The following tables present the details of reclassifications out of accumulated other comprehensive loss for the six months ended June 30, 2020 and 2019: Six Months Ended June 30, 2020 (In thousands) Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized losses on sales of securities $ (730 ) Net investment gain Defined benefit plan adjustments – actuarial losses (481 ) (1) Total reclassifications for the period, before tax (1,211 ) Tax benefit 339 Total reclassifications for the period, net of tax $ (872 ) (1) Six Months Ended June 30, 2019 (In thousands) Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gains on sales of securities $ 161 Net investment gain Defined benefit plan adjustments – actuarial losses (393 ) (1) Total reclassifications for the period, before tax (232 ) Tax benefit 80 Total reclassifications for the period, net of tax $ (152 ) (1) The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the three months ended June 30, 2020 and 2019: Three Months Ended Three Months Ended June 30, 2020 June 30, 2019 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gain on available-for-sale securities $ 1,191 $ (310 ) $ 881 $ 243 $ (63 ) $ 180 Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss) (686 ) 178 (508 ) (99 ) 26 (73 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss) 277 (86 ) 191 217 (67 ) 150 Foreign currency translation adjustment 1,899 — 1,899 533 — 533 Total Other Comprehensive Income (Loss) $ 2,681 $ (218 ) $ 2,463 $ 894 $ (104 ) $ 790 The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the six months ended June 30, 2020 and 2019: Six Months Ended Six Months Ended June 30, 2020 June 30, 2019 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gain (loss) on available-for-sale securities $ (68 ) $ 18 $ (50 ) $ 555 $ (144 ) $ 411 Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss) 730 (190 ) 540 (161 ) 42 (119 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss) 481 (149 ) 332 393 (122 ) 271 Foreign currency translation adjustment 249 — 249 (627 ) — (627 ) Total Other Comprehensive Income (Loss) $ 1,392 $ (321 ) $ 1,071 $ 160 $ (224 ) $ (64 )

Earnings (Loss) Per Share

Earnings (Loss) Per Share	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Earnings (Loss) Per Share	15. EARNINGS (LOSS) PER SHARE A summary of the calculation of basic and diluted earnings (loss) per share for the three and six months ended June 30, 2020 and 2019 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands, except per share amounts) 2020 2019 2020 2019 Numerator Net income (loss) $ 752 $ 3,995 $ (9,217 ) $ 4,765 Denominator Weighted average number of shares – basic 47,958 47,802 47,957 47,792 Effect of dilutive securities Stock options — 7 — — PSUs, RSUs and restricted stock 296 227 — 147 Weighted average number of shares – diluted 48,254 48,036 47,957 47,939 Earnings (loss) per share – basic $ 0.02 $ 0.08 $ (0.19 ) $ 0.10 Earnings (loss) per share – diluted $ 0.02 $ 0.08 $ (0.19 ) $ 0.10 For the three months ended June 30, 2020 and 2019, 0.1 million and 15 thousand shares, respectively, and for the six months ended June 30, 2020 and 2019, 0.2 million and 0.1 million shares, respectively, of unvested PSUs, RSUs and restricted stock were excluded from the calculation of diluted earnings per share due to their anti-dilutive effect. For the three months ended June 30, 2020 and 2019, 4.1 million and 1.9 million stock options, respectively, and for the six months ended June 30, 2020 and 2019, 4.9 million and 2.3 million stock options, respectively, were outstanding but were not included in the computation of diluted earnings per share. These stock options were excluded because their exercise prices were greater than the average market price of the common shares during the quarter, making them anti-dilutive under the treasury stock method.

Segment Information

Segment Information	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Segment Information	16. SEGMENT INFORMATION The chief operating decision maker regularly reviews the Company’s financial performance based on two reportable segments: (1) Network Solutions and (2) Services & Support. Network Solutions includes hardware and software products and next-generation virtualized solutions used in service provider or business networks, as well as prior-generation products. Services & Support includes a portfolio of maintenance, network installation and solution integration services, which include hosted cloud services and subscription services. The performance of our segments is evaluated based on gross profit; therefore, selling, general and administrative expenses, research and development expenses, interest and dividend income, interest expense, net investment gain (loss), other income (expense) and (provision) benefit for income taxes are reported on a Company-wide basis only. There is no inter-segment revenue. Asset information by reportable segment is not produced and, therefore, is not reported. The following tables present information about the sales and gross profit of our reportable segments for the three and six months ended June 30, 2020 and 2019. Three Months Ended June 30, 2020 June 30, 2019 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 111,323 $ 47,252 $ 139,167 $ 58,992 Services & Support 17,392 6,220 17,224 6,023 Total $ 128,715 $ 53,472 $ 156,391 $ 65,015 Six Months Ended June 30, 2020 June 30, 2019 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 208,695 $ 92,998 $ 264,989 $ 114,080 Services & Support 34,543 12,074 35,193 11,547 Total $ 243,238 $ 105,072 $ 300,182 $ 125,627 Sales by Category In addition to our reporting segments, revenue is also reported for the following three categories – Access & Aggregation, Subscriber Solutions & Experience and Traditional & Other Products. The table below presents sales information by category for the three and six months ended June 30, 2020 and 2019: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Access & Aggregation $ 82,776 $ 109,421 $ 148,742 $ 209,199 Subscriber Solutions & Experience 40,393 40,502 82,572 77,255 Traditional & Other Products 5,546 6,468 11,924 13,728 Total $ 128,715 $ 156,391 $ 243,238 $ 300,182 Sales by Geographic Area The following table presents sales information by geographic area for the three and six months ended June 30, 2020 and 2019: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 United States $ 84,458 $ 75,288 $ 163,449 $ 147,816 International 44,257 81,103 79,789 152,366 Total $ 128,715 $ 156,391 $ 243,238 $ 300,182

Liability for Warranty Returns

Liability for Warranty Returns	6 Months Ended
	Jun. 30, 2020
Product Warranties Disclosures [Abstract]
Liability for Warranty Returns	17. LIABILITY FOR WARRANTY RETURNS Our products generally include warranties of 90 days to five years for product defects. Warranty returns are accrued at the time revenue is recognized based on an estimate of the cost to repair or replace the defective products. We engage in extensive product quality programs and processes, including actively monitoring and evaluating the quality of our component suppliers. Products continue to become more complex in both size and functionality as many of our product offerings migrate from line card applications to total systems. The increasing complexity of products will cause warranty incidences, when they arise, to be more costly. Estimates regarding future warranty obligations may change due to product failure rates, material usage and other rework costs incurred in correcting a product failure. In addition, from time to time, specific warranty accruals may be recorded if unforeseen problems arise. Should actual experience relative to these factors be worse than estimated, additional warranty expense will be incurred. Alternatively, if actual costs incurred are less than estimated, a portion of the warranty reserves will be reversed in future periods. The liability for warranty obligations totaled $7.3 million and $8.4 million as of June 30, 2020 and December 31, 2019, respectively, and are included in accrued expenses and other liabilities in the accompanying Condensed Consolidated Balance Sheets. A reconciliation of warranty expense and related write-off activity for the three and six months ended June 30, 2020 and 2019 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Balance at beginning of period $ 7,635 $ 8,802 $ 8,394 $ 8,623 Plus: Amounts charged to cost and expenses 393 1,849 338 2,980 Less: Deductions (734 ) (1,679 ) (1,438 ) (2,631 ) Balance at end of period $ 7,294 $ 8,972 $ 7,294 $ 8,972

Commitments and Contingencies

Commitments and Contingencies	6 Months Ended
	Jun. 30, 2020
Commitments And Contingencies Disclosure [Abstract]
Commitments and Contingencies	18. COMMITMENTS AND CONTINGENCIES Securities Class Action Lawsuit On October 17, 2019, a purported stockholder class action lawsuit, captioned Burbridge v. ADTRAN, Inc. et al. The lawsuit claims that the defendants made materially false and misleading statements regarding, and/or failed to disclose material adverse facts about, the Company’s business, operations and prospects, specifically relating to the Company’s internal control over financial reporting, excess and obsolete inventory reserves, financial results and demand from certain customers. The lawsuit was transferred to the U.S. District Court for the Northern District of Alabama on January 7, 2020, and co-lead plaintiffs have been appointed to represent the putative class. The plaintiffs filed an amended complaint on April 30, 2020. The defendants filed a motion to dismiss the amended complaint on June 17, 2020. The p We deny the allegations in the complaint, as amended, and intend to vigorously defend against this lawsuit. At this time, we are unable to predict the outcome of or estimate the possible loss or range of loss, if any, associated with this lawsuit. Shareholder Derivative Lawsuit On March 31, 2020, a shareholder derivative suit, captioned Johnson (Derivatively on behalf of ADTRAN) v. T. Stanton, M. Foliano, R. Shannon, and Board of Directors and its defendants disagree with the claims made in the complaint, and the defendants intend to vigorously defend against this lawsuit. At this time, we are unable to predict the outcome of or estimate the possible loss or range of loss, if any, associated with this lawsuit. Other Legal Matters In addition to the litigation described above, from time to time we are subject to or otherwise involved in various lawsuits, claims, investigations and legal proceedings that arise out of or are incidental to the conduct of our business (collectively, “Legal Matters”), including those relating to employment matters, patent rights, regulatory compliance matters, stockholder claims, and contractual and other commercial disputes. Such Legal Matters, even if not meritorious, could result in the expenditure of significant financial and managerial resources. Additionally, an unfavorable outcome in any legal matter, including in a patent dispute, could require the Company to pay damages, entitle claimants to other relief, such as royalties, or could prevent the Company from selling some of its products in certain jurisdictions. While the Company cannot predict with certainty the results of the Legal Matters in which it is currently involved, the Company does not expect that the ultimate outcome of such Legal Matters will individually or in the aggregate have a material adverse effect on its business, results of operations, financial condition or cash flows. Performance Bonds Certain contracts, customers and jurisdictions in which we do business require us to provide various guarantees of performance such as bid bonds, performance bonds and customs bonds. As of June 30, 2020 and December 31, 2019, we had commitments related to these bonds totaling $11.3 million and $9.3 million, respectively, which expire at various dates through August 2024. Although the triggering events vary from contract to contract, in general we would only be liable for the amount of these guarantees in the event of default under each contract, the probability of which we believe is remote. In June of 2020, the Company entered into a letter of credit with a bank to guarantee performance obligations under a contract with a customer. The letter of credit is secured by a pledge of collateral in the amount of $5.0 million, of which $1.2 million is included in restricted cash and $3.8 million is included in long-term investments on the Condensed Consolidated Balance Sheet as of June 30, 2020. Currently, the Company is required to maintain a minimum collateral value of approximately $5.0 million. The minimum collateral value will increase over time as the Company reaches certain milestones in the contract. The maximum collateral value required under the contract will be approximately $12.0 million, and this is expected to occur in February 2021. This minimum collateral value will increase further if the Company changes the mix of investments away from restricted cash and into other investments. Any shortfalls in the minimum collateral value are required to be restored by the Company from available cash and cash equivalents, short-term investments or long-term investments. The obligations under the customer contract will be performed over multiple years. The collateral under the letter of credit will be released when all obligations under the customer contract have been met. As of June 30, 2020, the Company was in compliance with all contractual requirements under the letter of credit. Investment Commitment We have committed to invest up to an aggregate of $5.0 million in a private equity fund, of which $4.9 million has been contributed as of June 30, 2020.

Current Expected Credit Losses

Current Expected Credit Losses	6 Months Ended
	Jun. 30, 2020
Credit Loss [Abstract]
Current Expected Credit Losses	19. CURRENT EXPECTED CREDIT LOSSES Under ASC 326 – Financial Instruments – Credit Losses Assets Measured at Amortized Cost Accounts Receivable The Company records accounts receivable in the normal course of business as products are shipped or services are performed and invoiced, but payment has not yet been remitted by the customer. As of January 1, 2020 and June 30, 2020, the Company’s outstanding accounts receivable balance was $90.5 million and $95.3 million, respectively. The Company assessed the need for an allowance for credit losses related to its outstanding accounts receivable as of June 30, 2020 and January 1, 2020 using the historical loss-rate method as well as assessing asset-specific risks. The Company’s historical losses related to accounts receivable have been immaterial as evidenced by its historical allowance and write-offs due to uncollectability. The assessment of asset-specific risks included the evaluation of relevant available information, from internal and external sources, relating to current conditions that may affect a customer’s ability to pay, such as the customer’s current financial condition, credit rating by geographic location, as provided by a third party and/or by customer, if needed, and overall macro-economic conditions in which the customer operates. The Company pooled assets by geographic location to determine if an allowance should be applied to its accounts receivable balance, assessing the specific country risk rating and overall economics of that particular country. If elevated risk existed, or customer specific risk indicated the accounts receivable balance was at risk, the Company further analyzed the need for an allowance related to specific accounts receivable balances. Additionally, the Company determined that significant changes to customer country risk rating from period-to-period and from the end of the prior year to the end of the current quarter would require further review and analysis by the Company. Accounts receivable balances are considered past due when payment has not been received by the date indicated on the relevant invoice or based on agreed upon terms between the customer and the Company. No allowance for credit loss was recorded on January 1, 2020 (the “implementation date”) or during the three and six months ended June 30, 2020 related to accounts receivable. The Company’s allowance for credit losses related to accounts receivable was $38 thousand as of June 30, 2020 and December 31, 2019, all of which was expensed prior to January 1, 2020. Contract Assets The Company records contract assets when it has recognized revenue but has not yet billed the customer. As of January 1, 2020 and June 30, 2020, the Company’s outstanding contract asset balance was $2.8 million and $1.0 million, respectively, which is included in other receivables on the Condensed Consolidated Balance Sheets as of December 31, 2019 and June 30, 2020. The Company assessed the need for an allowance for credit losses related to its outstanding contract assets as of June 30, 2020 and January 1, 2020 using the historical loss-rate method as well as asset-specific risks. The Company’s historical losses related to contract assets receivable have been immaterial as evidenced by historical write-offs due to uncollectability. Asset-specific risk included the evaluation of relevant available information, from internal and external sources, relating to current conditions that may affect a customer’s ability to pay once invoiced, such as the customer’s financial condition, credit rating by geographic location as provided by a third party and/or by customer, if needed, and overall macro-economic conditions in which the customer operates. The Company pooled assets by geographic location to determine if an allowance should be applied to its contract asset balance, assessing the specific country risk rating and overall economics of that particular country. If elevated risk existed, or customer specific risk indicated the contract balance was at risk, the Company further analyzed the need for an allowance related to specific customer balances. Additionally, the Company determined that significant changes to customer country risk rating from period-to-period and from the end of the prior year to the end of the current quarter would be subject to further review and analysis by the Company. No allowance for credit loss was recorded on the implementation date or during the three and six months ended June 30, 2020 related to contract assets. Net Investment in Sales-Type Leases The Company is the lessor in sales-type lease arrangements for network equipment. As of January 1, 2020 and June 30, 2020, the Company’s outstanding net investment in sales-type leases was $1.6 million and $1.1 million, respectively, which is included in other receivables and other assets on the Condensed Consolidated Balance Sheets as of December 31, 2019 and June 30, 2020. The Company assessed the need for an allowance for credit losses related to future receivables under its outstanding sales-type leases as of June 30, 2020 and January 1, 2020 using the historical loss-rate method as well as asset-specific risks. The Company’s historical losses related to contract assets receivable have been immaterial as evidenced by historical write-offs due to uncollectability. Asset-specific risk included the evaluation of relevant available information, from internal and external sources, relating to current conditions that may affect a customer’s ability to pay once invoiced, such as the customer’s financial condition, credit rating by geographic location as provided by a third party and/or by customer, if needed, and overall macro-economic conditions in which the customer operates. The following table presents amortized cost basis in sales-type leases based on payment activity: Sales-Type Leases Amortized Cost Basis by Origination Year (In thousands) 2020 2019 2018 2017 2016 Prior Total Payment performance Performing $ 43 $ 261 $ 500 $ 187 $ 127 $ 14 $ 1,132 Non-performing — — — — — — — Total $ 43 $ 261 $ 500 $ 187 $ 127 $ 14 $ 1,132 Sales-type lease receivables are considered past due when payment has not been received based on agreed upon terms between the customer and the Company. No allowance for credit loss was recorded on the implementation date or during the three and six months ended June 30, 2020 related to sales-type leases. Secured Loan Receivable The Company has a secured loan receivable totaling $0.9 million as of June 30, 2020 and January 1, 2020, which originated in February 2019, and is included in long-term investments on the Condensed Consolidated Balance Sheets as of June 30, 2020 and December 31, 2019. The Company assessed the need for an allowance for credit loss related to its secured loan receivable as of June 30, 2020 and January 1, 2020 using the historical loss-rate method as well as asset-specific risks. There have been no historical losses related to this receivable. Asset-specific risks included the evaluation of relevant available information, from internal and external sources, relating to current conditions that may affect the customer’s ability to repay the loan upon maturity, such as the customer’s current financial condition, credit rating specific to the customer as determined by a third party and current overall economic conditions, as well as a Company valuation prepared by a third party which was based on reasonable and supportable forecasts as provided by management. Accrued interest receivable on the secured loan receivable, which is included in other receivables on the Condensed Consolidated Balance Sheets as of June 30, 2020 and December 31, 2019, totaled $24 thousand and $0 as of January 1, 2020 and June 30, 2020, respectively, and was excluded from the estimate of credit losses for both periods based on the Company’s accounting policy election. No allowance for credit loss was recorded on the implementation date or during the three and six months ended June 30, 2020 related to the secured loan receivable. Off-Balance Sheet Arrangements The Company did not have any off-balance sheet arrangements as of January 1, 2020 or June 30, 2020. As of January 1, 2020 and June 30, 2020, the Company’s available-for-sale debt securities totaled $37.7 million and $42.6 million, respectively. These securities were analyzed at the individual investment level, by CUSIP, to limit credit losses, if applicable, to reflect only the amount by which the fair value of the security was less than its amortized cost. The Company noted that, as of January 1, 2020 and June 30, 2020, there was no intent to sell any of its available-for-sale debt securities before maturity, and, therefore, the Company assessed the need for an allowance for each of its available-for-sale debt securities in which the fair value was less than its amortized cost as of January 1, 2020 and June 30, 2020. The Company had 43 positions in available-for-sale debt securities that were in an unrealized loss position as of June 30, 2020, which are presented in the table below: (In thousands) Continuous Unrealized Loss Position for Less than 12 Months Continuous Unrealized Loss Position for 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate bonds 865 (1 ) — — 865 (1 ) Municipal fixed-rate bonds — — — — — — Asset-backed bonds 331 (4 ) — — 331 (4 ) Mortgage/Agency-backed bonds 1,017 (12 ) — — 1,017 (12 ) U.S. government bonds 900 — — — 900 — Foreign government 75 — — — 75 — Commercial paper — — — — — — Total $ 3,188 $ (17 ) $ — $ — $ 3,188 $ (17 ) The following table outlines the available-for-sale debt securities in an unrealized loss position as of January 1, 2020: (In thousands) Continuous Unrealized Loss Position for Less than 12 Months Continuous Unrealized Loss Position for 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate bonds 203 — — — 203 — Municipal fixed-rate bonds 930 — — — 930 — Asset-backed bonds 797 (3 ) — — 797 (3 ) Mortgage/Agency-backed bonds 2,594 (6 ) 136 (2 ) 2,730 (8 ) U.S. government bonds 4,070 (9 ) — — 4,070 (9 ) Total $ 8,594 $ (18 ) $ 136 $ (2 ) $ 8,730 $ (20 ) For those available-for-sale debt securities whose fair value was less than its amortized cost basis, the Company analyzed additional criteria such as adverse conditions specifically related to the security, an industry or geographic area, failure of the issuer of the security to make scheduled interest or principal payments, if applicable, and any changes to the rating of the security by a rating agency to determine if a credit loss existed. The Company used information provided by its investment manager to determine if any scheduled interest or principal payments had not been received and used a third party to determine if any changes to credit ratings had occurred. The Company noted that all principal and interest payments had been received as scheduled and that there had been no changes in credit ratings year-over-year or period-over-period that warranted further review. No allowance for credit loss was recorded on the implementation date or during the three and six months ended June 30, 2020 related to the Company’s available-for-sale debt securities.

Restructuring

Restructuring	6 Months Ended
	Jun. 30, 2020
Restructuring And Related Activities [Abstract]
Restructuring	20. RESTRUCTURING During the second half of 2019, the Company implemented a restructuring plan to realign its expense structure with the reduction in revenue experienced in recent years and overall Company objectives. Management assessed the efficiency of operations and, in turn, consolidated locations and personnel, among other things, where possible. As part of this restructuring plan, the Company announced plans to reduce its overall operating expenses, both in the U.S. and internationally. In February 2019, the Company announced the restructuring of a certain portion of its workforce predominantly in Germany, which included the closure of the Company’s office location in Munich, Germany accompanied by relocation or severance benefits for the affected employees. Voluntary early retirement was offered to certain other employees, which was announced in March 2019. A reconciliation of the beginning and ending restructuring liability, which is included in accrued wages and benefits in the Condensed Consolidated Balance Sheets as of June 30, 2020 and December 31, 2019, is as follows: Three Months Ended Six Months Ended (In thousands) June 30, 2020 June 30, 2020 Balance at beginning of period $ 133 $ 1,568 Plus: Amounts charged to cost and expense 1,192 1,745 Less: Amounts paid (967 ) (2,955 ) Balance as of June 30, 2020 $ 358 $ 358 (In thousands) December 31, 2019 Balance as of December 31, 2018 $ 185 Plus: Amounts charged to cost and expense 6,014 Less: Amounts paid (4,631 ) Balance as of December 31, 2019 $ 1,568 Restructuring expenses included in the Condensed Consolidated Statements of Income (Loss) were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Selling, general and administrative expenses $ 489 $ 703 $ 572 $ 1,547 Research and development expenses 681 647 1,117 1,231 Cost of sales 22 50 56 685 Total restructuring expenses $ 1,192 $ 1,400 $ 1,745 $ 3,463 The following table represents the components of restructuring expense by geographic area: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Domestic $ 1,192 $ 541 $ 1,743 $ 825 International — 859 2 2,638 Total restructuring expenses $ 1,192 $ 1,400 $ 1,745 $ 3,463

Subsequent Events

Subsequent Events	6 Months Ended
	Jun. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	21. SUBSEQUENT EVENTS On August 5, 2020, we announced that our Board of Directors declared a quarterly cash dividend of $0.09 per common share to be paid to the Company’s stockholders of record as of the close of business on August 20, 2020. The payment date will be September 3, 2020 in the aggregate amount of approximately $4.3 million.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	6 Months Ended
	Jun. 30, 2020
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of ADTRAN ® In the opinion of management, all adjustments necessary to fairly state these interim statements have been recorded and are of a normal and recurring nature. The results of operations for an interim period are not necessarily indicative of the results for the full year. The interim financial statements should be read in conjunction with the consolidated financial statements and notes thereto included in ADTRAN’s Annual Report on Form 10-K for the year ended December 31, 2019, filed with the SEC on February 25, 2020.
Use of Estimates	Use of Estimates The preparation of financial statements in conformity with U.S. GAAP requires management to make estimates and assumptions that affect the reported amounts of assets and liabilities, the disclosure of contingent assets and liabilities at the date of the financial statements, and the reported amounts of revenue and expense during the reporting period. The more significant estimates include excess and obsolete inventory reserves, warranty reserves, customer rebates, determination and accrual of deferred revenue components of multi-element sales agreements, estimated costs to complete obligations associated with deferred and accrued revenues and network installations, estimated income tax provision and income tax contingencies, fair value of stock-based compensation, assessment of goodwill and other intangibles for impairment, estimated lives of intangible assets, estimated pension liability and fair value of investments. Actual amounts could differ significantly from these estimates. We assessed certain accounting matters that generally require consideration of forecasted financial information in context with the information reasonably available to us and the unknown future impacts of the novel coronavirus (“COVID-19”) as of June 30, 2020 and through the date of this report. The accounting matters assessed included, but were not limited to, the allowance for doubtful accounts, current estimated credit losses, stock-based compensation, carrying value of goodwill, intangibles and other long-lived assets, financial assets, valuation allowances for tax assets and revenue recognition. While there was not a material impact to our consolidated financial statements as of and for the quarter ended June 30, 2020 resulting from these assessments, future conditions related to the magnitude and duration of the COVID-19 pandemic, as well as other factors, could result in material impacts to our consolidated financial statements in future reporting periods.
Correction of Immaterial Misstatements	Correction of Immaterial Misstatements During the three months ended June 30, 2019, the Company determined that there was an immaterial misstatement of its excess and obsolete inventory reserves in its previously issued annual and interim financial statements. The Company corrected this misstatement by recognizing a $0.8 million out-of-period adjustment during the three months ended June 30, 2019, which increased its excess and obsolete inventory reserve and cost of goods sold for the period. For the six months ended June 30, 2019, the out-of-period adjustment was a cumulative $0.2 million reduction in its excess and obsolete inventory reserve and cost of goods sold. In addition, the Company determined that a cash inflow related to an insurance recovery was incorrectly classified as a cash flow from operations instead of a cash flow from investing activities within the unaudited Condensed Consolidated Statement of Cash Flows for the three months ended March 31, 2019. The Company corrected this misstatement in the Unaudited Condensed Consolidated Statement of Cash Flows for the six months ended June 30, 2019 to correctly reflect the $1.0 million insurance recovery as a cash inflow from investing activities. During the first quarter of 2020, it was determined that certain investments held in the Company’s stock for a deferred compensation plan accounted for as a Rabbi trust were incorrectly classified as long-term investments with the fair value of such investments incorrectly marked to market at each period end rather than classified as treasury stock held at historical cost. This plan has been in existence since 2011. The Company corrected this misstatement as an out-of-period adjustment in the three months ended March 31, 2020 by remeasuring the investment assets to their historical cost basis through the recording of a net investment gain of $1.5 million in the unaudited Condensed Consolidated Statement of Income (Loss) and then correcting the classification by decreasing the long-term investment balance at its remeasured cost basis of $2.8 million to treasury stock in the unaudited Condensed Consolidated Balance Sheet as of March 31, 2020. Management has determined that this misstatement was not material to any of its previously issued financial statements and that correction of the misstatement is also not expected to be material to the 2020 annual financial results on either a quantitative or qualitative basis.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements During 2020, we adopted the following accounting standards, which had the following impacts on our consolidated financial statements: In June 2016, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update (“ASU”) 2016-13, Financial Instruments – Credit Losses (Topic 326): Measurement of Credit Losses on Financial Instruments. Codification Improvements to Topic 326 Financial Instruments – Credit Losses, Codification Improvements to Topic 326, Financial Instruments–Credit Losses, Topic 815, Derivatives and Hedging, and Topic 825, Financial Instruments, Financial Instruments – Credit Losses (Topic 326): Targeted Transition Relief, Codification Improvements to Topic 326, Financial Instruments – Credit Losses elected to carry forward legacy disclosures for comparative periods and did not adjust the comparative period financial information. Additionally, the Company made an accounting policy election, at the class of financing receivable, not to measure the allowance for credit losses for accrued interest receivables, as the Company writes off the uncollectable accrued interest receivable by reversing any previously recorded interest income in a timely manner (as soon as these amounts are determined to be uncollectable). The adoption of this standard did not have a material effect on our consolidated financial statements. See Note 19 for additional information. In January 2017, the FASB issued ASU 2017-04, Intangibles – Goodwill and Other (Topic 350): Simplifying the Test for Goodwill Impairment 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, Fair Value Measurement. Concepts Statement No. 8 — Conceptual Framework for Financial Reporting — Chapter 8 — Notes to Financial Statements 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 clarifies certain aspects of ASU 2015-05, Customer’s Accounting for Fees Paid in a Cloud Computing Arrangement. Specifically, ASU 2018-15 aligns the requirements for capitalizing implementation costs incurred in a hosting arrangement that is a service contract with the requirements for capitalizing implementations costs incurred to develop or obtain internal use software. The Company adopted ASU 2018-15 on January 1, 2020, retrospectively. The adoption of this standard resulted in a reclass ification of $ 5.6 million from property, plant and equipment to other assets for certain previously capitalized costs related to information technology implementation projects that had not yet been placed in service on the C ondensed C onsolidated B alance S heet s as of June 30 , 2020 and December 31, 2019 . There was no impact to previously reported net cash provided by (used in) operations on the statement of cash flows and no impact to the statements of income (loss) as no portion of the capitalized asset was depreciated in prior periods. The following table illustrates the impact of adoption of ASU 2018-15 on the Condensed Consolidated Balance Sheet as of December 31, 2019: As of December 31, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Balance Sheet Property, plant and equipment, net $ 73,708 $ (5,622 ) $ 68,086 Other assets $ 14,261 $ 5,622 $ 19,883 The following table illustrates the impact of adoption of ASU 2018-15 on the Condensed Consolidated Statement of Income for the three and six months ended June 30, 2019 and the Condensed Consolidated Statement of Cash Flows for six months ended June 30, 2019: Three months ended June 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Income (Loss) Net income $ 3,995 $ — $ 3,995 Six months ended June 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Income (Loss) Net income $ 4,765 $ — $ 4,765 Condensed Consolidated Statement of Cash Flows Net cash provided by operating activities $ 11,007 $ — $ 11,007 In December 2019, the FASB issued ASU 2019-12, Income Taxes (Topic 740): Simplifying the Accounting for Income Taxes,
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In August 2018, the FASB ASU Compensation – Retirement Benefits – Defined Benefit Plans – General (Subtopic 715-20): Disclosure Framework – Changes to the Disclosure Requirements for Defined Benefit Plans,

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	6 Months Ended
	Jun. 30, 2020
ASU 2018-15 [Member]
Schedule of Impact of Adoption of ASU 2018-15 on Condensed Consolidated Balance Sheet, Statement of Income and Cash Flows	The following table illustrates the impact of adoption of ASU 2018-15 on the Condensed Consolidated Balance Sheet as of December 31, 2019: As of December 31, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Balance Sheet Property, plant and equipment, net $ 73,708 $ (5,622 ) $ 68,086 Other assets $ 14,261 $ 5,622 $ 19,883 The following table illustrates the impact of adoption of ASU 2018-15 on the Condensed Consolidated Statement of Income for the three and six months ended June 30, 2019 and the Condensed Consolidated Statement of Cash Flows for six months ended June 30, 2019: Three months ended June 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Income (Loss) Net income $ 3,995 $ — $ 3,995 Six months ended June 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Income (Loss) Net income $ 4,765 $ — $ 4,765 Condensed Consolidated Statement of Cash Flows Net cash provided by operating activities $ 11,007 $ — $ 11,007

Cash ,Cash Equivalents and Re_2

Cash ,Cash Equivalents and Restricted Cash (Tables)	6 Months Ended
	Jun. 30, 2020
Cash And Cash Equivalents [Abstract]
Summary of Reconciliation of Cash, Cash Equivalents and Restricted	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the consolidated balance sheet that sum to the total of the same such amounts shown in the consolidated statement of cash flows: (In thousands) June 30, 2020 Cash and cash equivalents $ 69,059 Restricted cash 1,186 Cash, cash equivalents and restricted cash $ 70,245

Revenue (Tables)

Revenue (Tables)	6 Months Ended
	Jun. 30, 2020
Revenue From Contract With Customer [Abstract]
Disaggregate of Revenue by Reportable Segment and Revenue Category	The following tables disaggregate revenue by reportable segment and revenue category for the three and six months ended June 30, 2020 and 2019: Three Months Ended June 30, 2020 June 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 69,721 $ 13,055 $ 82,776 $ 96,262 $ 13,159 $ 109,421 Subscriber Solutions & Experience 38,081 2,312 40,393 38,444 2,058 40,502 Traditional & Other Products 3,521 2,025 5,546 4,461 2,007 6,468 Total $ 111,323 $ 17,392 $ 128,715 $ 139,167 $ 17,224 $ 156,391 Six Months Ended June 30, 2020 June 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 122,776 $ 25,966 $ 148,742 $ 181,935 $ 27,264 $ 209,199 Subscriber Solutions & Experience 78,064 4,508 82,572 73,163 4,092 77,255 Traditional & Other Products 7,855 4,069 11,924 9,891 3,837 13,728 Total $ 208,695 $ 34,543 $ 243,238 $ 264,989 $ 35,193 $ 300,182 The table below presents sales information by category for the three and six months ended June 30, 2020 and 2019: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Access & Aggregation $ 82,776 $ 109,421 $ 148,742 $ 209,199 Subscriber Solutions & Experience 40,393 40,502 82,572 77,255 Traditional & Other Products 5,546 6,468 11,924 13,728 Total $ 128,715 $ 156,391 $ 243,238 $ 300,182
Information about Receivables, Contract Assets, and Unearned Revenue from Contracts with Customers	The following table provides information about receivables, contract assets and unearned revenue from contracts with customers: (In thousands) June 30, 2020 December 31, 2019 Accounts receivable, net $ 95,335 $ 90,531 Contract assets (1) $ 1,028 $ 2,812 Unearned revenue $ 12,090 $ 11,963 Non-current unearned revenue $ 6,166 $ 6,012 (1) Included in other receivables on the Condensed Consolidated Balance Sheets.

Income Taxes (Tables)

Income Taxes (Tables)	6 Months Ended
	Jun. 30, 2020
Income Tax Disclosure [Abstract]
Summary of Supplemental Balance Sheet Information Related to Deferred Tax Assets	Supplemental balance sheet information related to deferred tax assets as of June 30, 2020 and December 31, 2019 is as follows: June 30, 2020 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 50,164 $ (50,164 ) $ — International 9,603 (2,030 ) 7,573 Total $ 59,767 $ (52,194 ) $ 7,573 December 31, 2019 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 46,266 $ (46,266 ) $ — International 9,911 (2,350 ) 7,561 Total $ 56,177 $ (48,616 ) $ 7,561

Pension Benefit Plan (Tables)

Pension Benefit Plan (Tables)	6 Months Ended
	Jun. 30, 2020
Compensation And Retirement Disclosure [Abstract]
Summarization of Components of Net Periodic Pension Cost	The following table summarizes the components of net periodic pension cost related to a defined benefit pension plan covering employees in certain foreign countries for the three and six months ended June 30, 2020 and 2019: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Service cost $ 307 $ 368 $ 617 $ 743 Interest cost 108 159 216 321 Expected return on plan assets (407 ) (348 ) (817 ) (703 ) Amortization of actuarial losses 235 199 472 402 Net periodic pension cost $ 243 $ 378 $ 488 $ 763

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	6 Months Ended
	Jun. 30, 2020
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Stock-Based Compensation Expense Related to Stock Options, PSUs, RSUs and Restricted Stock	The following table summarizes stock-based compensation expense related to stock options, performance stock units (“PSUs”), restricted stock units (“RSUs”) and restricted stock for the three and six months ended June 30, 2020 and 2019: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Stock-based compensation expense included in cost of sales $ 87 $ 85 $ 202 $ 189 Selling, general and administrative expense 971 662 2,046 1,725 Research and development expense 597 707 1,198 1,399 Stock-based compensation expense included in operating expenses 1,568 1,369 3,244 3,124 Total stock-based compensation expense 1,655 1,454 3,446 3,313 Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock (394 ) (332 ) (821 ) (775 ) Total stock-based compensation expense, net of tax $ 1,261 $ 1,122 $ 2,625 $ 2,538
Summary of PSUs, RSUs and Restricted Stock Outstanding	The following table summarizes PSUs, RSUs and restricted stock outstanding as of December 31, 2019 and June 30, 2020 and the changes that occurred during the six months ended June 30, 2020. Number of Shares (in thousands) Weighted Avg. Grant Date Fair Value (per share) Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2019 1,891 $ 14.58 PSUs, RSUs and restricted stock granted 399 $ 8.21 PSUs, RSUs and restricted stock vested (13 ) $ 12.32 PSUs, RSUs and restricted stock forfeited (518 ) $ 19.27 Unvested PSUs, RSUs and restricted stock outstanding, June 30, 2020 1,759 $ 11.78
Summary of Stock Options Outstanding	The following table summarizes stock options outstanding as of December 31, 2019 and June 30, 2020 and the changes that occurred during the six months ended June 30, 2020: Number of Stock Options (in thousands) Weighted Avg. Exercise Price (per share) Weighted Avg. Remaining Contractual Life (in years) Aggregate Intrinsic Value (in thousands) Stock options outstanding, December 31, 2019 3,572 $ 22.88 3.4 $ — Stock options exercised — $ — Stock options forfeited — $ — Stock options expired (265 ) $ 21.20 Stock options outstanding, June 30, 2020 3,307 $ 22.93 2.9 $ — Stock options exercisable, June 30, 2020 3,305 $ 22.93 2.9 $ —

Investments (Tables)

Investments (Tables)	6 Months Ended
	Jun. 30, 2020
Investments Debt And Equity Securities [Abstract]
Debt Securities and Other Investments, Included on Condensed Consolidated Balance Sheet and Recorded at Fair Value	Debt Securities and Other Investments As of June 30, 2020, the following debt securities and other investments were included on the Condensed Consolidated Balance Sheet and recorded at fair value: Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 13,747 $ 168 $ (1 ) $ 13,914 Municipal fixed-rate bonds 2,379 21 — 2,400 Asset-backed bonds 7,600 86 (4 ) 7,682 Mortgage/Agency-backed bonds 7,944 152 (12 ) 8,084 U.S. government bonds 7,935 211 — 8,146 Foreign government bonds 540 — — 540 Commercial paper 1,120 4 — 1,124 Variable-rate demand notes 300 — — 300 Other 442 — — 442 Available-for-sale debt securities held at fair value $ 42,007 $ 642 $ (17 ) $ 42,632 A s of December 31, 2019 , the following debt securities and other investments were included on the Condensed Consolidated Balance sheet and recorded at fair value: Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 9,304 $ 80 $ — $ 9,384 Municipal fixed-rate bonds 930 — — 930 Asset-backed bonds 6,867 26 (3 ) 6,890 Mortgage/Agency-backed bonds 6,944 26 (8 ) 6,962 U.S. government bonds 12,311 21 (9 ) 12,323 Foreign government bonds 372 — (1 ) 371 Variable-rate demand notes 800 — — 800 Available-for-sale debt securities held at fair value $ 37,528 $ 153 $ (21 ) $ 37,660
Contractual Maturities of Debt Securities and Other Investments	As of June 30, 2020, contractual maturities related to debt securities and other investments were as follows: (In thousands) Corporate bonds Municipal fixed-rate bonds Asset- backed bonds Mortgage/ Agency- backed bonds U.S. government bonds Foreign government bonds Commercial paper Variable-rate demand notes Other Less than one year $ 5,441 $ 738 $ 465 $ 146 $ — $ — $ 1,124 $ — $ 442 One to two years 2,926 528 465 603 1,638 75 — — — Two to three years 5,547 757 1,141 1,528 6,065 465 — — — Three to five years — 377 3,932 — 443 — — — — Five to ten years — — 982 1,890 — — — — — More than ten years — — 697 3,917 — — — 300 — Total $ 13,914 $ 2,400 $ 7,682 $ 8,084 $ 8,146 $ 540 $ 1,124 $ 300 $ 442
Gross Realized Gains and Losses on Sale of Debt Securities	The following table presents gross realized gains and losses related to our debt securities: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Gross realized gains on debt securities $ 190 $ 8 $ 233 $ 49 Gross realized losses on debt securities (19 ) (14 ) (39 ) (33 ) Total gain recognized, net $ 171 $ (6 ) $ 194 $ 16
Realized and Unrealized Gains and Losses related to Marketable Equity Securities	Realized and unrealized gains and losses related to marketable equity securities for the three and six months ended June 30, 2020 and 2019 were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Realized gains (losses) on equity securities sold $ 328 $ (49 ) $ (2,108 ) $ (63 ) Unrealized gains (losses) on equity securities held 9,353 2,540 889 8,458 Total gain (loss) recognized, net $ 9,681 $ 2,491 $ (1,219 ) $ 8,395
Cash Equivalents and Investments held at Fair Value	The Company’s cash equivalents and investments held at fair value are categorized into this hierarchy as follows: Fair Value Measurements as of June 30, 2020 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,697 $ 1,697 $ — $ — U.S. government securities 1,250 1,250 — — Commercial paper 100 — 100 — Available-for-sale debt securities Corporate bonds 13,914 — 13,914 — Municipal fixed-rate bonds 2,400 — 2,400 — Asset-backed bonds 7,682 — 7,682 — Mortgage/Agency-backed bonds 8,084 — 8,084 — U.S. government bonds 8,146 8,146 — — Foreign government securities 540 — 540 — Commercial paper 1,124 — 1,124 — Variable-rate demand notes 300 — 300 — Other 442 — — 442 Marketable equity securities Marketable equity securities – various industries 26,116 26,116 — — Deferred compensation plan assets 20,468 20,468 — — Other investments 1,223 1,223 — — Total $ 93,486 $ 58,900 $ 34,144 $ 442 Fair Value Measurements as of December 31, 2019 Using (In thousands) Fair Value Quoted Prices in Active Market for Identical Assets (Level 1) Significant Other Observable Inputs (Level 2) Significant Unobservable Inputs (Level 3) Cash equivalents Money market funds $ 1,309 $ 1,309 $ — $ — Available-for-sale debt securities Corporate bonds 9,384 — 9,384 — Municipal fixed-rate bonds 930 — 930 — Asset-backed bonds 6,890 — 6,890 — Mortgage/Agency-backed bonds 6,962 — 6,962 — U.S. government bonds 12,323 12,323 — — Foreign government bonds 371 — 371 — Variable-rate demand notes 800 — 800 — Marketable equity securities Marketable equity securities – various industries 35,501 35,501 — — Equity in escrow 298 298 — — Deferred compensation plan assets 21,698 21,698 — — Other investments 2,442 2,442 — — Total $ 98,908 $ 73,571 $ 25,337 $ —

Inventory (Tables)

Inventory (Tables)	6 Months Ended
	Jun. 30, 2020
Inventory Disclosure [Abstract]
Components of Inventory	As of June 30, 2020 and December 31, 2019, inventory consisted of the following: June 30, December 31, (In thousands) 2020 2019 Raw materials $ 37,057 $ 36,987 Work in process 610 1,085 Finished goods 68,464 60,233 Total inventory $ 106,131 $ 98,305

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	6 Months Ended
	Jun. 30, 2020
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	At June 30, 2020 and December 31, 2019, property, plant and equipment consisted of the following: June 30, December 31, (In thousands) 2020 2019 Land $ 4,575 $ 4,575 Building and land improvements 34,897 34,797 Building 68,155 68,157 Furniture and fixtures 19,972 19,959 Computer hardware and software 69,564 68,777 Engineering and other equipment 131,785 130,430 Total property, plant and equipment 328,948 326,695 Less: accumulated depreciation (263,754 ) (258,609 ) Total property, plant and equipment, net $ 65,194 $ 68,086

Intangible Assets (Tables)

Intangible Assets (Tables)	6 Months Ended
	Jun. 30, 2020
Intangible Assets Net Excluding Goodwill [Abstract]
Summary of Intangible Assets	Intangible assets as of June 30, 2020 and December 31, 2019 consisted of the following: June 30, 2020 December 31, 2019 (In thousands) Gross Carrying Amount Accumulated Amortization Net Book Value Gross Carrying Amount Accumulated Amortization Net Book Value Customer relationships $ 20,742 $ (6,690 ) $ 14,052 $ 22,356 $ (7,233 ) $ 15,123 Developed technology 8,200 (1,977 ) 6,223 10,170 (3,379 ) 6,791 Licensed technology 5,900 (1,503 ) 4,397 5,900 (1,174 ) 4,726 Supplier relationships 2,800 (2,800 ) — 2,800 (2,508 ) 292 Licensing agreements 560 (116 ) 444 560 (79 ) 481 Patents 500 (260 ) 240 500 (226 ) 274 Trade names 210 (111 ) 99 310 (176 ) 134 Total $ 38,912 $ (13,457 ) $ 25,455 $ 42,596 $ (14,775 ) $ 27,821
Estimated Future Amortization Expense Related to Intangible Assets	As of June 30, 2020, estimated future amortization expense of intangible assets was as follows: (In thousands) 2020 $ 2,076 2021 4,095 2022 3,472 2023 3,320 2024 3,227 Thereafter 9,265 Total $ 25,455

Leases (Tables)

Leases (Tables)	6 Months Ended
	Jun. 30, 2020
Leases [Abstract]
Schedule of Operating Lease Assets and Operating Lease Liabilities	As of June 30, 2020 and December 31, 2019, the Company’s operating lease assets and operating lease liabilities were as follows: (In thousands) Classification June 30, 2020 December 31, 2019 Assets Operating lease asset Other assets $ 5,973 $ 8,452 Total lease asset $ 5,973 $ 8,452 Liabilities Current operating lease liability Accrued expenses $ 1,854 $ 2,676 Non-current operating lease liability Other non-current liabilities 4,134 5,818 Total lease liability $ 5,988 $ 8,494
Components of Lease Expense included in Condensed Consolidated Statement of Income (Loss)	Components of lease expense included in the Condensed Consolidated Statements of Income (Loss) for the three and six months ended June 30, 2020 and 2019 were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Selling, general and administrative expenses $ 271 $ 349 $ 598 $ 698 Research and development expenses 251 430 676 884 Cost of sales 26 17 47 33 Total operating lease expense $ 548 $ 796 $ 1,321 $ 1,615
Schedule of Maturity of Operating Lease Liabilities	As of June 30, 2020 and December 31, 2019, operating lease liabilities included on the Condensed Consolidated Balance Sheets by future maturity were as follows: (In thousands) June 30, 2020 December 31, 2019 2020 $ 1,048 $ 2,856 2021 1,815 2,412 2022 1,514 1,705 2023 1,110 1,160 2024 478 482 Thereafter 264 264 Total lease payments 6,229 8,879 Less: Interest (241 ) (385 ) Present value of lease liabilities $ 5,988 $ 8,494
Schedule of Weighted Average Remaining Lease Terms and Weighted Average Discount Rates	The following table provides information about the weighted average lease terms and weighted average discount rates as of June 30, 2020 : As of June 30, 2020 Weighted average remaining lease term (in years) Operating leases with USD functional currency 2.5 Operating leases with Euro functional currency 4.0 Weighted average discount rate Operating leases with USD functional currency 4.46 % Operating leases with Euro functional currency 1.83 %
Schedule of Supplemental Cash Flow Information Related to Operating Leases	Supplemental cash flow information related to operating leases is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Cash paid for amounts included in the measurement of operating lease assets / liabilities Cash used in operating activities related to operating leases $ 770 $ 797 $ 1,477 $ 1,608 Right-of-use assets obtained in exchange for lease obligations $ 8 $ 9 $ 93 $ 10,396
Net Investment in Sales-Type Leases	We are the lessor in sales-type lease arrangements for network equipment, which have initial terms of up to five years, and consisted of the following as of June 30, 2020 and December 31, 2019: (In thousands) June 30, 2020 December 31, 2019 Current minimum lease payments receivable (1) $ 923 $ 1,201 Non-current minimum lease payments receivable (2) 566 889 Total minimum lease payments receivable 1,489 2,090 Less: Current unearned revenue 265 365 Less: Non-current unearned revenue 92 163 Net investment in sales-type leases $ 1,132 $ 1,562 (1) Included in other receivables on the Condensed Consolidated Balance Sheets. (2) Included in other assets on the Condensed Consolidated Balance Sheets.
Schedule of Components of Gross Profit Related to Sales-type Leases and Interest and Dividend Income Included in Condensed Consolidated Statements of Income (Loss)	C omponents of gross profit related to sales-type leases recognized at the lease commencement date and interest and dividend income included in the Condensed Consolidated Statements of Income (Loss) for the three and six months ended June 30, 2020 and 2019 were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Sales - Network Solutions $ 12 $ 109 $ 50 $ 1,621 Less: Cost of sales - Network Solutions 4 44 20 635 Gross profit $ 8 $ 65 $ 30 $ 986 Interest and dividend income $ 11 $ 99 $ 24 $ 186

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	6 Months Ended
	Jun. 30, 2020
Equity [Abstract]
Changes in Accumulated Other Comprehensive Loss, Net of Tax by Component	The following tables present the changes in accumulated other comprehensive loss, net of tax, by component for the three months ended June 30, 2020 and 2019: Three Months Ended June 30, 2020 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (1) Total As of March 31, 2020 $ (167 ) $ (9,085 ) $ (8,942 ) $ 385 $ (17,809 ) Other comprehensive income before reclassifications 881 — 1,899 — 2,780 Amounts reclassified from accumulated other comprehensive income (loss) (508 ) 191 — — (317 ) Net current period other comprehensive income 373 191 1,899 — 2,463 As of June 30, 2020 $ 206 $ (8,894 ) $ (7,043 ) $ 385 $ (15,346 ) Three Months Ended June 30, 2019 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (1) Total As of March 31, 2019 $ (378 ) $ (7,920 ) $ (6,972 ) $ 385 $ (14,885 ) Other comprehensive income before reclassifications 180 — 533 — 713 Amounts reclassified from accumulated other comprehensive income (loss) (73 ) 150 — — 77 Net current period other comprehensive income 107 150 533 — 790 As of June 30, 2019 $ (271 ) $ (7,770 ) $ (6,439 ) $ 385 $ (14,095 ) (1) The following tables present the changes in accumulated other comprehensive loss, net of tax , by component for the six months ended June 30, 2020 and 2019 : Six Months Ended June 30, 2020 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (1) Total As of December 31, 2019 $ (284 ) $ (9,226 ) $ (7,292 ) $ 385 $ (16,417 ) Other comprehensive income (loss) before reclassifications (50 ) — 249 — 199 Amounts reclassified from accumulated other comprehensive income 540 332 — — 872 Net current period other comprehensive income 490 332 249 — 1,071 As of June 30, 2020 $ 206 $ (8,894 ) $ (7,043 ) $ 385 $ (15,346 ) Six Months Ended June 30, 2019 (In thousands) Unrealized Gains (Losses) on Available- for-Sale Securities Defined Benefit Plan Adjustments Foreign Currency Adjustments ASU 2018-02 Adoption (1) Total As of December 31, 2018 $ (563 ) $ (8,041 ) $ (5,812 ) $ — $ (14,416 ) Other comprehensive income (loss) before reclassifications 411 — (627 ) — (216 ) Amounts reclassified from accumulated other comprehensive income (loss) (119 ) 271 — — 152 Amounts reclassified to retained earnings (1) — — — 385 385 Net current period other comprehensive income (loss) 292 271 (627 ) 385 321 As of June 30, 2019 $ (271 ) $ (7,770 ) $ (6,439 ) $ 385 $ (14,095 ) (1)
Reclassifications Out of Accumulated Other Comprehensive Loss	The following tables present the details of reclassifications out of accumulated other comprehensive loss for the three months ended June 30, 2020 and 2019: Three Months Ended June 30, 2020 (In thousands) Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gains on sales of securities $ 686 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (277 ) (1) Total reclassifications for the period, before tax 409 Tax expense (92 ) Total reclassifications for the period, net of tax $ 317 (1) Three Months Ended June 30, 2019 (In thousands) Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gains on sales of securities $ 99 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (217 ) (1) Total reclassifications for the period, before tax (118 ) Tax benefit 41 Total reclassifications for the period, net of tax $ (77 ) (1) The following tables present the details of reclassifications out of accumulated other comprehensive loss for the six months ended June 30, 2020 and 2019: Six Months Ended June 30, 2020 (In thousands) Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized losses on sales of securities $ (730 ) Net investment gain Defined benefit plan adjustments – actuarial losses (481 ) (1) Total reclassifications for the period, before tax (1,211 ) Tax benefit 339 Total reclassifications for the period, net of tax $ (872 ) (1) Six Months Ended June 30, 2019 (In thousands) Amount Reclassified from Accumulated Other Comprehensive Income (Loss) Affected Line Item in the Statement Where Net Income Is Presented Unrealized gains (losses) on available-for-sale securities: Net realized gains on sales of securities $ 161 Net investment gain Defined benefit plan adjustments – actuarial losses (393 ) (1) Total reclassifications for the period, before tax (232 ) Tax benefit 80 Total reclassifications for the period, net of tax $ (152 ) (1)
Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Loss)	The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the three months ended June 30, 2020 and 2019: Three Months Ended Three Months Ended June 30, 2020 June 30, 2019 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gain on available-for-sale securities $ 1,191 $ (310 ) $ 881 $ 243 $ (63 ) $ 180 Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss) (686 ) 178 (508 ) (99 ) 26 (73 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss) 277 (86 ) 191 217 (67 ) 150 Foreign currency translation adjustment 1,899 — 1,899 533 — 533 Total Other Comprehensive Income (Loss) $ 2,681 $ (218 ) $ 2,463 $ 894 $ (104 ) $ 790 The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the six months ended June 30, 2020 and 2019: Six Months Ended Six Months Ended June 30, 2020 June 30, 2019 (In thousands) Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Before-Tax Amount Tax (Expense) Benefit Net-of-Tax Amount Unrealized gain (loss) on available-for-sale securities $ (68 ) $ 18 $ (50 ) $ 555 $ (144 ) $ 411 Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss) 730 (190 ) 540 (161 ) 42 (119 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss) 481 (149 ) 332 393 (122 ) 271 Foreign currency translation adjustment 249 — 249 (627 ) — (627 ) Total Other Comprehensive Income (Loss) $ 1,392 $ (321 ) $ 1,071 $ 160 $ (224 ) $ (64 )

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	6 Months Ended
	Jun. 30, 2020
Earnings Per Share [Abstract]
Summary of Calculation of Basic and Diluted Earnings (Loss) Per Share	A summary of the calculation of basic and diluted earnings (loss) per share for the three and six months ended June 30, 2020 and 2019 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands, except per share amounts) 2020 2019 2020 2019 Numerator Net income (loss) $ 752 $ 3,995 $ (9,217 ) $ 4,765 Denominator Weighted average number of shares – basic 47,958 47,802 47,957 47,792 Effect of dilutive securities Stock options — 7 — — PSUs, RSUs and restricted stock 296 227 — 147 Weighted average number of shares – diluted 48,254 48,036 47,957 47,939 Earnings (loss) per share – basic $ 0.02 $ 0.08 $ (0.19 ) $ 0.10 Earnings (loss) per share – diluted $ 0.02 $ 0.08 $ (0.19 ) $ 0.10

Segment Information (Tables)

Segment Information (Tables)	6 Months Ended
	Jun. 30, 2020
Segment Reporting [Abstract]
Sales and Gross Profit of Reportable Segments	The following tables present information about the sales and gross profit of our reportable segments for the three and six months ended June 30, 2020 and 2019. Three Months Ended June 30, 2020 June 30, 2019 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 111,323 $ 47,252 $ 139,167 $ 58,992 Services & Support 17,392 6,220 17,224 6,023 Total $ 128,715 $ 53,472 $ 156,391 $ 65,015 Six Months Ended June 30, 2020 June 30, 2019 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 208,695 $ 92,998 $ 264,989 $ 114,080 Services & Support 34,543 12,074 35,193 11,547 Total $ 243,238 $ 105,072 $ 300,182 $ 125,627
Disaggregate of Revenue by Reportable Segment and Revenue Category	The following tables disaggregate revenue by reportable segment and revenue category for the three and six months ended June 30, 2020 and 2019: Three Months Ended June 30, 2020 June 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 69,721 $ 13,055 $ 82,776 $ 96,262 $ 13,159 $ 109,421 Subscriber Solutions & Experience 38,081 2,312 40,393 38,444 2,058 40,502 Traditional & Other Products 3,521 2,025 5,546 4,461 2,007 6,468 Total $ 111,323 $ 17,392 $ 128,715 $ 139,167 $ 17,224 $ 156,391 Six Months Ended June 30, 2020 June 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 122,776 $ 25,966 $ 148,742 $ 181,935 $ 27,264 $ 209,199 Subscriber Solutions & Experience 78,064 4,508 82,572 73,163 4,092 77,255 Traditional & Other Products 7,855 4,069 11,924 9,891 3,837 13,728 Total $ 208,695 $ 34,543 $ 243,238 $ 264,989 $ 35,193 $ 300,182 The table below presents sales information by category for the three and six months ended June 30, 2020 and 2019: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Access & Aggregation $ 82,776 $ 109,421 $ 148,742 $ 209,199 Subscriber Solutions & Experience 40,393 40,502 82,572 77,255 Traditional & Other Products 5,546 6,468 11,924 13,728 Total $ 128,715 $ 156,391 $ 243,238 $ 300,182
Sales Information by Geographic Area	The following table presents sales information by geographic area for the three and six months ended June 30, 2020 and 2019: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 United States $ 84,458 $ 75,288 $ 163,449 $ 147,816 International 44,257 81,103 79,789 152,366 Total $ 128,715 $ 156,391 $ 243,238 $ 300,182

Liability for Warranty Returns

Liability for Warranty Returns (Tables)	6 Months Ended
	Jun. 30, 2020
Product Warranties Disclosures [Abstract]
Reconciliation of Warranty Expense and Related Write-off Activity	A reconciliation of warranty expense and related write-off activity for the three and six months ended June 30, 2020 and 2019 is as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Balance at beginning of period $ 7,635 $ 8,802 $ 8,394 $ 8,623 Plus: Amounts charged to cost and expenses 393 1,849 338 2,980 Less: Deductions (734 ) (1,679 ) (1,438 ) (2,631 ) Balance at end of period $ 7,294 $ 8,972 $ 7,294 $ 8,972

Current Expected Credit Losses

Current Expected Credit Losses (Tables)	6 Months Ended
	Jun. 30, 2020
Credit Loss [Abstract]
Amortized Cost Basis in Sales-Type Leases based on Payment Activity	The following table presents amortized cost basis in sales-type leases based on payment activity: Sales-Type Leases Amortized Cost Basis by Origination Year (In thousands) 2020 2019 2018 2017 2016 Prior Total Payment performance Performing $ 43 $ 261 $ 500 $ 187 $ 127 $ 14 $ 1,132 Non-performing — — — — — — — Total $ 43 $ 261 $ 500 $ 187 $ 127 $ 14 $ 1,132
Available-for-Sale Debt Securities in Unrealized Loss Position	The Company had 43 positions in available-for-sale debt securities that were in an unrealized loss position as of June 30, 2020, which are presented in the table below: (In thousands) Continuous Unrealized Loss Position for Less than 12 Months Continuous Unrealized Loss Position for 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate bonds 865 (1 ) — — 865 (1 ) Municipal fixed-rate bonds — — — — — — Asset-backed bonds 331 (4 ) — — 331 (4 ) Mortgage/Agency-backed bonds 1,017 (12 ) — — 1,017 (12 ) U.S. government bonds 900 — — — 900 — Foreign government 75 — — — 75 — Commercial paper — — — — — — Total $ 3,188 $ (17 ) $ — $ — $ 3,188 $ (17 ) The following table outlines the available-for-sale debt securities in an unrealized loss position as of January 1, 2020: (In thousands) Continuous Unrealized Loss Position for Less than 12 Months Continuous Unrealized Loss Position for 12 Months or Greater Total Fair Value Unrealized Losses Fair Value Unrealized Losses Fair Value Unrealized Losses Corporate bonds 203 — — — 203 — Municipal fixed-rate bonds 930 — — — 930 — Asset-backed bonds 797 (3 ) — — 797 (3 ) Mortgage/Agency-backed bonds 2,594 (6 ) 136 (2 ) 2,730 (8 ) U.S. government bonds 4,070 (9 ) — — 4,070 (9 ) Total $ 8,594 $ (18 ) $ 136 $ (2 ) $ 8,730 $ (20 )

Restructuring (Tables)

Restructuring (Tables)	6 Months Ended
	Jun. 30, 2020
Restructuring And Related Activities [Abstract]
Schedule of Reconciliation of Restructuring Liability	A reconciliation of the beginning and ending restructuring liability, which is included in accrued wages and benefits in the Condensed Consolidated Balance Sheets as of June 30, 2020 and December 31, 2019, is as follows: Three Months Ended Six Months Ended (In thousands) June 30, 2020 June 30, 2020 Balance at beginning of period $ 133 $ 1,568 Plus: Amounts charged to cost and expense 1,192 1,745 Less: Amounts paid (967 ) (2,955 ) Balance as of June 30, 2020 $ 358 $ 358 (In thousands) December 31, 2019 Balance as of December 31, 2018 $ 185 Plus: Amounts charged to cost and expense 6,014 Less: Amounts paid (4,631 ) Balance as of December 31, 2019 $ 1,568
Schedule of Components of Restructuring Expenses	Restructuring expenses included in the Condensed Consolidated Statements of Income (Loss) were as follows: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Selling, general and administrative expenses $ 489 $ 703 $ 572 $ 1,547 Research and development expenses 681 647 1,117 1,231 Cost of sales 22 50 56 685 Total restructuring expenses $ 1,192 $ 1,400 $ 1,745 $ 3,463 The following table represents the components of restructuring expense by geographic area: Three Months Ended Six Months Ended June 30, June 30, (In thousands) 2020 2019 2020 2019 Domestic $ 1,192 $ 541 $ 1,743 $ 825 International — 859 2 2,638 Total restructuring expenses $ 1,192 $ 1,400 $ 1,745 $ 3,463

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 01, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Summary Of Significant Accounting Policy [Line Items]
Life insurance proceeds received						$ 1,000
Tax benefit in other comprehensive income (loss)		$ 218		$ 104	$ 321	224
ASU 2018-15 [Member] | Reclassification of Property, Plant and Equipment to Other Assets [Member]
Summary Of Significant Accounting Policy [Line Items]
Effect on adoption of ASU	$ 5,600
Adjustments for New Accounting Principle, Early Adoption [Member]
Summary Of Significant Accounting Policy [Line Items]
Tax benefit in other comprehensive income (loss)					$ (100)
Excess, Obsolete Inventory Reserve and Cost of Goods [Member]
Summary Of Significant Accounting Policy [Line Items]
Amount of revision				800		$ 200
Errors in Operating Activity [Member]
Summary Of Significant Accounting Policy [Line Items]
Amount of revision				$ 1,000
Overstatement Long-term Investment Balance at Remeasured Cost Basis [Member]
Summary Of Significant Accounting Policy [Line Items]
Amount of revision			$ 2,800
Errors in Net Investment Gain [Member]
Summary Of Significant Accounting Policy [Line Items]
Amount of revision			$ 1,500

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Schedule of Impact of Adoption of ASU 2018-15 on Condensed Consolidated Balance Sheet (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, net	$ 65,194	$ 68,086
Other assets	$ 18,225	19,883
ASU 2018-15 [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, net		68,086
Other assets		19,883
Pre-Adoption [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, net		73,708
Other assets		14,261
Effect of Adoption [Member] | ASU 2018-15 [Member]
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, net		(5,622)
Other assets		$ 5,622

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Schedule of Impact of Adoption of ASU 2018-15 on Condensed Consolidated Statement of Income and Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Summary Of Significant Accounting Policy [Line Items]
Net income	$ 752	$ (9,969)	$ 3,995	$ 770	$ (9,217)	$ 4,765
Net cash provided by operating activities					$ 1,681	11,007
ASU 2018-15 [Member]
Summary Of Significant Accounting Policy [Line Items]
Net income			3,995			4,765
Net cash provided by operating activities						11,007
Pre-Adoption [Member]
Summary Of Significant Accounting Policy [Line Items]
Net income			$ 3,995			4,765
Net cash provided by operating activities						$ 11,007

Cash, Cash Equivalents and Rest

Cash, Cash Equivalents and Restricted Cash - Summary of Reconciliation of Cash, Cash Equivalents and Restricted (Details) - USD ($)	Jun. 30, 2020	Dec. 31, 2019	Jun. 30, 2019
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 69,059,000	$ 73,773,000
Restricted cash	1,186,000		$ 0
Cash, cash equivalents and restricted cash	$ 70,245,000

Cash, Cash Equivalents and Re_2

Cash, Cash Equivalents and Restricted Cash - Additional Information (Detail) - USD ($)	Jun. 30, 2020	Jun. 30, 2019
Cash And Cash Equivalents [Abstract]
Restricted cash	$ 1,186,000	$ 0

Revenue - Additional Informatio

Revenue - Additional Information (Detail)	3 Months Ended		6 Months Ended
	Jun. 30, 2020USD ($)	Jun. 30, 2019USD ($)	Jun. 30, 2020USD ($)Category	Jun. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Revenue [Line Items]
Number of categories | Category			3
Remaining performance obligations	$ 0		$ 0
Recognized revenue	2,400,000	$ 3,600,000	8,100,000	$ 10,500,000
Other Than Maintenance Services
Revenue [Line Items]
Remaining performance obligations	$ 16,000,000		$ 16,000,000		$ 13,600,000

Revenue - Disaggregate of Reven

Revenue - Disaggregate of Revenue by Reportable Segment and Revenue Category (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation Of Revenue [Line Items]
Revenue	$ 128,715	$ 156,391	$ 243,238	$ 300,182
Reclassification of Property, Plant and Equipment to Other Assets [Member]
Disaggregation Of Revenue [Line Items]
Revenue	82,776	109,421	148,742	209,199
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	40,393	40,502	82,572	77,255
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	5,546	6,468	11,924	13,728
Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	111,323	139,167	208,695	264,989
Network Solutions [Member] | Reclassification of Property, Plant and Equipment to Other Assets [Member]
Disaggregation Of Revenue [Line Items]
Revenue	69,721	96,262	122,776	181,935
Network Solutions [Member] | Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	38,081	38,444	78,064	73,163
Network Solutions [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	3,521	4,461	7,855	9,891
Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue	17,392	17,224	34,543	35,193
Services & Support [Member] | Reclassification of Property, Plant and Equipment to Other Assets [Member]
Disaggregation Of Revenue [Line Items]
Revenue	13,055	13,159	25,966	27,264
Services & Support [Member] | Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	2,312	2,058	4,508	4,092
Services & Support [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 2,025	$ 2,007	$ 4,069	$ 3,837

Revenue - Additional Informat_2

Revenue - Additional Information (Detail1) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-07-01	Jun. 30, 2020
Revenue [Line Items]
Remaining performance obligations, percentage	62.00%
Remaining performance obligations, period	12 months

Revenue - Information about Rec

Revenue - Information about Receivables, Contract Assets, and Unearned Revenue from Contracts with Customers (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Revenue From Contract With Customer [Abstract]
Accounts receivable, net	$ 95,335	$ 90,500	$ 90,531
Contract assets	1,028	$ 2,800	2,812
Unearned revenue	12,090		11,963
Non-current unearned revenue	$ 6,166		$ 6,012

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Effective tax rate expense (benefit)	68.50%	17.30%	22.90%	6.20%
Income tax benefit, result of CARES act of 2020			$ 7,400
Effective tax rate reduction related to transfer pricing study		29.10%		29.10%
Deferred tax assets, gross	$ 59,767		59,767		$ 56,177
Valuation allowance established against deferred tax assets	52,194		52,194		48,616
Deferred tax assets	7,573		7,573		7,561
Domestic [Member]
Income Tax Disclosure [Line Items]
Valuation allowance established against deferred tax assets	3,600		3,600
Deferred tax assets, gross	50,164		50,164		46,266
Valuation allowance established against deferred tax assets	$ 50,164		$ 50,164		$ 46,266

Income Taxes - Summary of Suppl

Income Taxes - Summary of Supplemental Balance Sheet Information Related to Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	$ 59,767	$ 56,177
Valuation Allowance	(52,194)	(48,616)
Deferred Tax Assets, net	7,573	7,561
Domestic [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	50,164	46,266
Valuation Allowance	(50,164)	(46,266)
International [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	9,603	9,911
Valuation Allowance	(2,030)	(2,350)
Deferred Tax Assets, net	$ 7,573	$ 7,561

Pension Benefit Plan - Summariz

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 307	$ 368	$ 617	$ 743
Interest cost	108	159	216	321
Expected return on plan assets	(407)	(348)	(817)	(703)
Amortization of actuarial losses	235	199	472	402
Net periodic pension cost	$ 243	$ 378	$ 488	$ 763

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options, PSUs, RSUs and Restricted Stock (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,655	$ 1,454	$ 3,446	$ 3,313
Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock	(394)	(332)	(821)	(775)
Total stock-based compensation expense, net of tax	1,261	1,122	2,625	2,538
Stock-based Compensation Expense Included in Cost of Sales [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	87	85	202	189
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	971	662	2,046	1,725
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	597	707	1,198	1,399
Stock-based Compensation Expense Included in Operating Expenses [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,568	$ 1,369	$ 3,244	$ 3,124

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of PSUs, RSUs and Restricted Stock Outstanding (Detail) shares in Thousands	6 Months Ended
	Jun. 30, 2020$ / sharesshares
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, beginning balance | shares	1,891
Number of Shares, PSUs, RSUs and restricted stock granted | shares	399
Number of Shares, PSUs, RSUs and restricted stock vested | shares	(13)
Number of Shares, PSUs, RSUs and restricted stock forfeited | shares	(518)
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, ending balance | shares	1,759
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	$ 14.58
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	8.21
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	12.32
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	19.27
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	$ 11.78

Stock-Based Compensation (PSUs,

Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) $ in Millions	6 Months Ended
	Jun. 30, 2020USD ($)shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options available for issuance under stockholders-approved equity plan	3,400,000
2015 Employee Stock Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of additional shares of common stock granted	0
2010 Directors Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of additional shares of common stock granted	0
2020 Employee Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares of common stock authorized	2,800,000
Multiplier used when issuing PSUs, restricted stock and RSUs	1
Contractual term	10 years
2020 Directors Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of shares of common stock authorized	400,000
Multiplier used when issuing PSUs, restricted stock and RSUs	1
Contractual term	10 years
2010 Directors Stock Plan to 2020 Directors Stock Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Forfeiture of stock increase in issuance of common stock	1
Performance Stock Units (PSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share issued	300,000
Performance target period	3 years
Performance Stock Units (PSUs) [Member] | Minimum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of performance stock units granted	0.00%
Performance Stock Units (PSUs) [Member] | Maximum [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Percentage of performance stock units granted	142.80%
Market-Based PSUs, RSUs and Restricted Stock [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to other than options | $	$ 12.7
Recognition period of unvested compensation expense	2 years 6 months
PSUs, RSUs and Restricted Stock [Member] | 2020 Employee Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	4 years
PSUs, RSUs and Restricted Stock [Member] | 2015 Employee Incentive Plan to 2020 Employee Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Forfeiture of stock increase in issuance of common stock	2.5
Options | 2020 Employee Incentive Plan [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Vesting period	4 years

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Millions	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Number of Stock Options, Stock options outstanding, Beginning Balance	3,572
Number of Stock Options, Stock options expired	(265)
Number of Stock Options, Stock options outstanding, Ending Balance	3,307	3,572
Number of Stock Options, Stock options exercisable	3,305
Weighted Avg. Exercise Price, Stock options outstanding, Beginning Balance	$ 22.88
Weighted Avg. Exercise Price, Stock options expired	21.20
Weighted Avg. Exercise Price, Stock options outstanding, Ending Balance	22.93	$ 22.88
Weighted Avg. Exercise Price, Stock options exercisable	$ 22.93
Weighted Avg. Remaining Contractual Life In Years, Stock options outstanding	2 years 10 months 24 days	3 years 4 months 24 days
Weighted Avg. Remaining Contractual Life in Years, Stock options exercisable	2 years 10 months 24 days
Aggregate Intrinsic Value, Stock options outstanding	$ 0

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock Options) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Number of Stock options, granted	0	0	0	0
Aggregate intrinsic value based on fair market value	$ 0		$ 0
Total pre-tax intrinsic value of options exercised			0
Unvested Stock Options [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to non-vested stock options	$ 4		$ 4
Recognition period of unvested compensation expense			3 months 18 days

Investments - Debt Securities a

Investments - Debt Securities and Other Investments, Included on Condensed Consolidated Balance Sheet and Recorded at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 42,007		$ 37,528
Gross Unrealized Gains	642		153
Gross Unrealized Losses	(17)		(21)
Fair Value	42,632	$ 37,700	37,660
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	13,747		9,304
Gross Unrealized Gains	168		80
Gross Unrealized Losses	(1)
Fair Value	13,914		9,384
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	2,379		930
Gross Unrealized Gains	21
Fair Value	2,400		930
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,600		6,867
Gross Unrealized Gains	86		26
Gross Unrealized Losses	(4)		(3)
Fair Value	7,682		6,890
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,944		6,944
Gross Unrealized Gains	152		26
Gross Unrealized Losses	(12)		(8)
Fair Value	8,084		6,962
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,935		12,311
Gross Unrealized Gains	211		21
Gross Unrealized Losses			(9)
Fair Value	8,146		12,323
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	540		372
Gross Unrealized Losses			(1)
Fair Value	540		371
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,120
Gross Unrealized Gains	4
Fair Value	1,124
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	300		800
Fair Value	300		$ 800
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	442
Fair Value	$ 442

Investments - Contractual Matur

Investments - Contractual Maturities of Debt Securities and Other Investments (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Fair Value/Carrying Value	$ 42,632	$ 37,700	$ 37,660
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	5,441
One to two years	2,926
Two to three years	5,547
Available-for-sale debt securities, Fair Value/Carrying Value	13,914		9,384
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	738
One to two years	528
Two to three years	757
Three to five years	377
Available-for-sale debt securities, Fair Value/Carrying Value	2,400		930
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	465
One to two years	465
Two to three years	1,141
Three to five years	3,932
Five to ten years	982
More than ten years	697
Available-for-sale debt securities, Fair Value/Carrying Value	7,682		6,890
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	146
One to two years	603
Two to three years	1,528
Five to ten years	1,890
More than ten years	3,917
Available-for-sale debt securities, Fair Value/Carrying Value	8,084		6,962
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	1,638
Two to three years	6,065
Three to five years	443
Available-for-sale debt securities, Fair Value/Carrying Value	8,146		12,323
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
One to two years	75
Two to three years	465
Available-for-sale debt securities, Fair Value/Carrying Value	540		371
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	1,124
Available-for-sale debt securities, Fair Value/Carrying Value	1,124
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
More than ten years	300
Available-for-sale debt securities, Fair Value/Carrying Value	300		$ 800
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	442
Available-for-sale debt securities, Fair Value/Carrying Value	$ 442

Investments - Gross Realized Ga

Investments - Gross Realized Gains and Losses on Sale of Debt Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Investments Debt And Equity Securities [Abstract]
Gross realized gains on debt securities	$ 190	$ 8	$ 233	$ 49
Gross realized losses on debt securities	(19)	(14)	(39)	(33)
Total gain recognized, net	$ 171	$ (6)	$ 194	$ 16

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	3 Months Ended	6 Months Ended
	Mar. 31, 2019	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Purchase an available-for-sale debt securities with credit deterioration		$ 0
Transfer from investments	$ 3,400,000
Carrying value				$ 3,400,000
Note receivable, noncurrent		900,000	$ 900,000
Asset impairments		65,000
Carrying value of investment		1,800,000
Net Investment Gain (Loss) [Member]
Schedule of Investments [Line Items]
Asset impairments		1,600,000
Other Receivables [Member]
Schedule of Investments [Line Items]
Note receivable, current	$ 4,300,000	4,300,000		4,300,000
Asset impairments		0
Long-term Investments [Member]
Schedule of Investments [Line Items]
Note receivable, noncurrent		$ 900,000		$ 900,000
Investment [Member] | Issuer Concentration [Member] | Market Value of Total Investment Portfolio [Member]
Schedule of Investments [Line Items]
Investment concentration risk percentage		5.00%

Investments - Realized and Unre

Investments - Realized and Unrealized Gains and Losses related to Marketable Equity Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Investments Debt And Equity Securities [Abstract]
Realized gains (losses) on equity securities sold	$ 328	$ (49)	$ (2,108)	$ (63)
Unrealized gains (losses) on equity securities held	9,353	2,540	889	8,458
Total gain (loss) recognized, net	$ 9,681	$ 2,491	$ (1,219)	$ 8,395

Investments - Cash Equivalents

Investments - Cash Equivalents and Investments held at Fair Value (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	$ 42,632	$ 37,700	$ 37,660
Marketable equity securities	1,800
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Other investments	1,223		2,442
Total	93,486		98,908
Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Other investments	1,223		2,442
Total	58,900		73,571
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	34,144		25,337
Fair Value, Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	442
Money Market Funds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,697		1,309
Money Market Funds [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,697		1,309
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	8,146		12,323
U.S. Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,250
Available-for-sale debt securities	8,146		12,323
U.S. Government Bonds [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	1,250
Available-for-sale debt securities	8,146		12,323
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	1,124
Commercial Paper [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	100
Available-for-sale debt securities	1,124
Commercial Paper [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	100
Available-for-sale debt securities	1,124
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	13,914		9,384
Corporate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	13,914		9,384
Corporate Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	13,914		9,384
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	2,400		930
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	2,400		930
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	2,400		930
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	7,682		6,890
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	7,682		6,890
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	7,682		6,890
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	8,084		6,962
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	8,084		6,962
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	8,084		6,962
Other [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	442
Other [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	442
Other [Member] | Fair Value, Measurements [Member] | Significant Unobservable Inputs (Level 3) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	442
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	26,116		35,501
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	26,116		35,501
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	540		371
Foreign Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	540		371
Foreign Government Bonds [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	540		371
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	300		800
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	300		800
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	300		800
Equity in Escrow [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities			298
Equity in Escrow [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities			298
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	20,468		21,698
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	$ 20,468		$ 21,698

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Raw materials	$ 37,057	$ 36,987
Work in process	610	1,085
Finished goods	68,464	60,233
Total inventory	$ 106,131	$ 98,305

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Jun. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Inventory valuation reserves	$ 35.9	$ 34.1

Property, Plant and Equipment -

Property, Plant and Equipment - Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Land	$ 4,575	$ 4,575
Building and land improvements	34,897	34,797
Building	68,155	68,157
Furniture and fixtures	19,972	19,959
Computer hardware and software	69,564	68,777
Engineering and other equipment	131,785	130,430
Total property, plant and equipment	328,948	326,695
Less: accumulated depreciation	(263,754)	(258,609)
Total property, plant and equipment, net	$ 65,194	$ 68,086

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Property Plant And Equipment [Abstract]
Impairment losses of long-lived assets			$ 0
Depreciation	$ 3,000,000	$ 3,100,000	$ 6,000,000	$ 6,200,000

Goodwill - Additional Informati

Goodwill - Additional Information (Detail) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill	$ 7,000,000	$ 7,000,000
Impairment of goodwill	0
Network Solutions [Member]
Goodwill [Line Items]
Goodwill	6,600,000	400,000
Services & Support [Member]
Goodwill [Line Items]
Goodwill	$ 6,600,000	$ 400,000

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 38,912	$ 42,596
Accumulated Amortization	(13,457)	(14,775)
Net Book Value	25,455	27,821
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	20,742	22,356
Accumulated Amortization	(6,690)	(7,233)
Net Book Value	14,052	15,123
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	8,200	10,170
Accumulated Amortization	(1,977)	(3,379)
Net Book Value	6,223	6,791
Licensed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,900	5,900
Accumulated Amortization	(1,503)	(1,174)
Net Book Value	4,397	4,726
Supplier Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	2,800	2,800
Accumulated Amortization	(2,800)	(2,508)
Net Book Value		292
Licensing Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	560	560
Accumulated Amortization	(116)	(79)
Net Book Value	444	481
Patent [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	500	500
Accumulated Amortization	(260)	(226)
Net Book Value	240	274
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	210	310
Accumulated Amortization	(111)	(176)
Net Book Value	$ 99	$ 134

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Intangible Assets Net Excluding Goodwill [Abstract]
Impairment losses of intangible assets	$ 0
Amortization expense	$ 1,000,000	$ 1,300,000	$ 2,400,000	$ 2,700,000

Intangible Assets - Estimated F

Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Finite Lived Intangible Assets Future Amortization Expense [Abstract]
2020	$ 2,076
2021	4,095
2022	3,472
2023	3,320
2024	3,227
Thereafter	9,265
Net Book Value	$ 25,455	$ 27,821

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lessor and Lessee Lease Description [Line Items]
Operating lease, option to extend, existence			true
Operating lease, option to terminate, existence			true
Short-term lease cost	$ 5	$ 100	$ 14,000	$ 300
Variable lease cost	100	$ 300	300	$ 400
Operating lease payments, option to extend	$ 500		$ 500
Minimum [Member]
Lessor and Lessee Lease Description [Line Items]
Operating lease, remaining lease terms			1 month
Operating lease, options to terminate term			3 months
Maximum [Member]
Lessor and Lessee Lease Description [Line Items]
Operating lease, remaining lease terms			5 years
Operating lease, renewal term	9 years		9 years
Lessor sales-type lease arrangement terms for network equipment	5 years		5 years

Leases - Schedule of Operating

Leases - Schedule of Operating Lease Assets and Operating Lease Liabilities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
ASSETS
Operating lease asset	$ 5,973	$ 8,452
Operating lease, right-of-use asset, statement of financial position [extensible list]	us-gaap:OtherAssetsNoncurrent	us-gaap:OtherAssetsNoncurrent
Liabilities
Current operating lease liability	$ 1,854	$ 2,676
Operating lease, liability, current, statement of financial position [extensible list]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Non-current operating lease liability	$ 4,134	$ 5,818
Operating lease, liability, noncurrent, statement of financial position [extensible list]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Total lease liability	$ 5,988	$ 8,494

Leases - Components of Lease Ex

Leases - Components of Lease Expense included in Condensed Consolidated Statement of Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Lessor Lease Description [Line Items]
Total operating lease expense	$ 548	$ 796	$ 1,321	$ 1,615
Selling, General and Administrative Expenses [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	271	349	598	698
Research and Development Expenses [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	251	430	676	884
Cost of Sales [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	$ 26	$ 17	$ 47	$ 33

Leases - Schedule of Maturity o

Leases - Schedule of Maturity of Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Operating Lease Liabilities Payments Due [Abstract]
2020	$ 1,048
2020		$ 2,856
2021	1,815	2,412
2022	1,514	1,705
2023	1,110	1,160
2024	478	482
Thereafter	264	264
Total lease payments	6,229	8,879
Less: Interest	(241)	(385)
Present value of lease liabilities	$ 5,988	$ 8,494

Leases - Schedule of Weighted A

Leases - Schedule of Weighted Average Remaining Lease Terms and Weighted Average Discount Rates (Detail)	Jun. 30, 2020
USD
Weighted average remaining lease term (in years)
Operating leases with functional currency	2 years 6 months
Weighted average discount rate
Operating leases with functional currency	4.46%
Euro
Weighted average remaining lease term (in years)
Operating leases with functional currency	4 years
Weighted average discount rate
Operating leases with functional currency	1.83%

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information Related to Operating Leases (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Cash paid for amounts included in the measurement of operating lease assets / liabilities
Cash used in operating activities related to operating leases	$ 770	$ 797	$ 1,477	$ 1,608
Right-of-use assets obtained in exchange for lease obligations	$ 8	$ 9	$ 93	$ 10,396

Leases - Net Investment in Sale

Leases - Net Investment in Sales-Type Leases (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Sales Type Leases Net Investment In Leases [Abstract]
Current minimum lease payments receivable	$ 923		$ 1,201
Non-current minimum lease payments receivable	566		889
Total minimum lease payments receivable	1,489		2,090
Less: Current unearned revenue	265		365
Less: Non-current unearned revenue	92		163
Net investment in sales-type leases	$ 1,132	$ 1,600	$ 1,562

Leases - Schedule of Components

Leases - Schedule of Components of Gross Profit Related to Sales-type Leases and Interest and Dividend Income Included in Condensed Consolidated Statements of Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Sales [Member] | Network Solutions [Member]
Lessor Lease Description [Line Items]
Sales type leases	$ 12	$ 109	$ 50	$ 1,621
Stock-based Compensation Expense Included in Cost of Sales [Member] | Network Solutions [Member]
Lessor Lease Description [Line Items]
Sales type leases	4	44	20	635
Gross Profit [Member]
Lessor Lease Description [Line Items]
Sales type leases	8	65	30	986
Interest and Dividend Income [Member]
Lessor Lease Description [Line Items]
Sales type leases	$ 11	$ 99	$ 24	$ 186

Alabama State Industrial Deve_2

Alabama State Industrial Development Authority Financing and Economic Incentives - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 02, 2020	Jun. 30, 2020	Dec. 31, 2019	Dec. 31, 2008	Jan. 13, 1995
Debt Instrument [Line Items]
Repayment of bond		$ 24,600
Taxable Revenue Bonds [Member]
Debt Instrument [Line Items]
Proceeds from state industrial development authority issued taxable bonds loaned to ADTRAN			$ 24,600	$ 50,000	$ 20,000
Percentage of interest on bond			2.00%
Maturity date of bond			Jan. 1, 2020
Repayment of bond	$ 24,600
Certificate of deposit			$ 25,600

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2020shares
Equity [Abstract]
Stock repurchased, shares	0
Additional shares authorized for purchase	2,500,000
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	5,000,000

Stockholders' Equity - Changes

Stockholders' Equity - Changes in Accumulated Other Comprehensive Loss, Net of Tax by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 363,715	$ 443,547	$ 380,426	$ 446,279
Other comprehensive income (loss) before reclassifications	2,780	713	199	(216)
Amounts reclassified from accumulated other comprehensive income (loss)	(317)	77	872	152
Amounts reclassified to retained earnings				385
Net current period other comprehensive income (loss)	2,463	790	1,071	321
Ending Balance	364,194	445,975	364,194	445,975
ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	385	385	385
Amounts reclassified to retained earnings				385
Net current period other comprehensive income (loss)				385
Ending Balance	385	385	385	385
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(167)	(378)	(284)	(563)
Other comprehensive income (loss) before reclassifications	881	180	(50)	411
Amounts reclassified from accumulated other comprehensive income (loss)	(508)	(73)	540	(119)
Net current period other comprehensive income (loss)	373	107	490	292
Ending Balance	206	(271)	206	(271)
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(9,085)	(7,920)	(9,226)	(8,041)
Amounts reclassified from accumulated other comprehensive income (loss)	191	150	332	271
Net current period other comprehensive income (loss)	191	150	332	271
Ending Balance	(8,894)	(7,770)	(8,894)	(7,770)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(8,942)	(6,972)	(7,292)	(5,812)
Other comprehensive income (loss) before reclassifications	1,899	533	249	(627)
Net current period other comprehensive income (loss)	1,899	533	249	(627)
Ending Balance	(7,043)	(6,439)	(7,043)	(6,439)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(17,809)	(14,885)	(16,417)	(14,416)
Ending Balance	$ (15,346)	$ (14,095)	$ (15,346)	$ (14,095)

Stockholders' Equity - Reclassi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Loss (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Income (Loss) Before Income Taxes	$ 2,387		$ 3,407		$ (11,950)	$ 4,485
Tax benefit (expense)	(1,635)		588		2,733	280
Net Income (Loss)	752	$ (9,969)	3,995	$ 770	(9,217)	4,765
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit plan adjustments – actuarial losses	(277)		(217)		(481)	(393)
Income (Loss) Before Income Taxes	409		(118)		(1,211)	(232)
Tax benefit (expense)	(92)		41		339	80
Net Income (Loss)	317		(77)		(872)	(152)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member] | Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gain (loss)	$ 686		$ 99		$ (730)	$ 161

Stockholders' Equity - Tax Effe

Stockholders' Equity - Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Equity [Abstract]
Unrealized gain (loss) on available-for-sale securities, Before-Tax Amount	$ 1,191		$ 243		$ (68)	$ 555
Unrealized gain (loss) on available-for-sale securities, Tax (Expense) Benefit	(310)		(63)		18	(144)
Unrealized gain (loss) on available-for-sale securities, Net-of-Tax Amount	881		180		(50)	411
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Before-Tax Amount	(686)		(99)		730	(161)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Tax (Expense) Benefit	178		26		(190)	42
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Net-of-Tax Amount	(508)		(73)		540	(119)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Before-Tax Amount	277		217		481	393
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Tax (Expense) Benefit	(86)		(67)		(149)	(122)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Net-of-Tax Amount	191		150		332	271
Foreign currency translation adjustment, Before-Tax Amount	1,899		533		249	(627)
Foreign currency translation adjustment, Net-of-Tax Amount	1,899		533		249	(627)
Total Other Comprehensive Income (Loss), Before-Tax Amount	2,681		894		1,392	160
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	(218)		(104)		(321)	(224)
Other Comprehensive Income (Loss), net of tax	$ 2,463	$ (1,392)	$ 790	$ (854)	$ 1,071	$ (64)

Earnings (Loss) Per Share - Sum

Earnings (Loss) Per Share - Summary of Calculation of Basic and Diluted Earnings (Loss) Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Numerator
Net income (loss)	$ 752	$ (9,969)	$ 3,995	$ 770	$ (9,217)	$ 4,765
Denominator
Weighted average number of shares – basic	47,958		47,802		47,957	47,792
Effect of dilutive securities
Stock options			7
PSUs, RSUs and restricted stock	296		227			147
Weighted average number of shares – diluted	48,254		48,036		47,957	47,939
Earnings (loss) per share – basic	$ 0.02		$ 0.08		$ (0.19)	$ 0.10
Earnings (loss) per share – diluted	$ 0.02		$ 0.08		$ (0.19)	$ 0.10

Earnings (Loss) Per Share - Add

Earnings (Loss) Per Share - Additional Information (Detail) - shares shares in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted earnings per share	4,100	1,900	4,900	2,300
Unvested Stock Options, PSUs, RSUs and Restricted Stock [Member]
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted earnings per share	100	15	200	100

Segment Information - Additiona

Segment Information - Additional Information (Detail)	6 Months Ended
	Jun. 30, 2020CategorySegment
Segment Reporting [Abstract]
Number of reportable segments | Segment	2
Number of categories | Category	3

Segment Information - Sales and

Segment Information - Sales and Gross Profit of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Segment Reporting Information [Line Items]
Sales	$ 128,715	$ 156,391	$ 243,238	$ 300,182
Gross Profit	53,472	65,015	105,072	125,627
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales	111,323	139,167	208,695	264,989
Gross Profit	47,252	58,992	92,998	114,080
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales	17,392	17,224	34,543	35,193
Gross Profit	$ 6,220	$ 6,023	$ 12,074	$ 11,547

Segment Information - Sales Inf

Segment Information - Sales Information by Category (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Disaggregation Of Revenue [Line Items]
Revenue	$ 128,715	$ 156,391	$ 243,238	$ 300,182
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	82,776	109,421	148,742	209,199
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	40,393	40,502	82,572	77,255
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 5,546	$ 6,468	$ 11,924	$ 13,728

Segment Information- Sales Info

Segment Information- Sales Information by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Revenue from External Customer [Line Items]
Sales	$ 128,715	$ 156,391	$ 243,238	$ 300,182
United States [Member]
Revenue from External Customer [Line Items]
Sales	84,458	75,288	163,449	147,816
International [Member]
Revenue from External Customer [Line Items]
Sales	$ 44,257	$ 81,103	$ 79,789	$ 152,366

Liability for Warranty Return_2

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Dec. 31, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018
Product Warranties Disclosures [Abstract]
Period of assurance-based warranty for product defects	90 days to five years
Liability for warranty obligations	$ 7,294	$ 7,635	$ 8,394	$ 8,972	$ 8,802	$ 8,623

Liability for Warranty Return_3

Liability for Warranty Returns - Summary of Warranty Expense and Related Write-Off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 7,635	$ 8,802	$ 8,394	$ 8,623
Plus: Amounts charged to cost and expenses	393	1,849	338	2,980
Less: Deductions	(734)	(1,679)	(1,438)	(2,631)
Balance at end of period	$ 7,294	$ 8,972	$ 7,294	$ 8,972

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Mar. 31, 2020Officer	Oct. 17, 2019Officer	Jun. 30, 2020USD ($)	Dec. 31, 2019USD ($)
Contingencies And Commitments [Line Items]
Commitments related to performance bonds			$ 11,300,000	$ 9,300,000
Commitments related to performance bonds expiration month and year			2024-08
Letter of credit secured by pledge of collateral amount			$ 5,000,000
Commitments towards private equity funds			4,900,000
Investment Commitments [Member]
Contingencies And Commitments [Line Items]
Aggregate investment committed in private equity funds			5,000,000
Restricted Cash
Contingencies And Commitments [Line Items]
Letter of credit secured by pledge of collateral amount			1,200,000
Long-term Investments [Member]
Contingencies And Commitments [Line Items]
Letter of credit secured by pledge of collateral amount			3,800,000
Minimum [Member]
Contingencies And Commitments [Line Items]
Collateral value required to be maintained			5,000,000
Maximum [Member]
Contingencies And Commitments [Line Items]
Collateral value required to be maintained			$ 12,000,000
Current Executive Officers [Member]
Contingencies And Commitments [Line Items]
Number of officers | Officer	2	2
Former Executive Officers [Member]
Contingencies And Commitments [Line Items]
Number of officers | Officer	1	1

Current Expected Credit Losse_2

Current Expected Credit Losses - Additional Information (Detail)	Jan. 01, 2020USD ($)	Jun. 30, 2020USD ($)Position	Jun. 30, 2020USD ($)Position	Dec. 31, 2019USD ($)
Financing Receivable Allowance For Credit Losses [Line Items]
Outstanding accounts receivable	$ 90,500,000	$ 95,335,000	$ 95,335,000	$ 90,531,000
Allowance for credit loss, accounts receivable	0	0	0
Allowance for credit losses, accounts receivable		38,000	38,000	38,000
Outstanding contract asset	2,800,000	1,028,000	1,028,000	2,812,000
Allowance for credit losses related to contract assets	0	0	0
Outstanding net investment in sales-type leases	1,600,000	1,132,000	1,132,000	1,562,000
Net investment in sales-type leases, allowance for credit loss	0	0	0
Secured loan receivable	900,000	900,000	900,000
Accrued interest receivable	100,000	100,000	100,000
Secured loan receivable, allowance for credit loss	0	0	0
Available-for-sale debt securities	37,700,000	$ 42,632,000	$ 42,632,000	$ 37,660,000
Number of positions in available-for-sale debt securities, unrealized loss position | Position		43	43
Available-for-sale, debt securities, allowance for credit loss	0	$ 0	$ 0
Secured Loans Receivable [Member]
Financing Receivable Allowance For Credit Losses [Line Items]
Loss related to secured loan receivable			0
Accrued interest receivable	$ 24,000	$ 0	$ 0

Current Expected Credit Losse_3

Current Expected Credit Losses - Amortized Cost Basis in Sales-Type Leases based on Payment Activity (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Sales Type Lease Net Investment In Lease Credit Quality Indicator [Line Items]
2020	$ 43
2019	261
2018	500
2017	187
2016	127
Prior	14
Net investment in sales-type leases	1,132	$ 1,600	$ 1,562
Payment Performance Performing
Sales Type Lease Net Investment In Lease Credit Quality Indicator [Line Items]
2020	43
2019	261
2018	500
2017	187
2016	127
Prior	14
Net investment in sales-type leases	$ 1,132

Current Expected Credit Losse_4

Current Expected Credit Losses - Available-for-Sale Debt Securities in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Jun. 30, 2020	Jan. 01, 2020
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	$ 3,188	$ 8,594
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(17)	(18)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value		136
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses		(2)
Total Fair Value	3,188	8,730
Total Unrealized Losses	(17)	(20)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	865	203
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(1)
Total Fair Value	865	203
Total Unrealized Losses	(1)
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value		930
Total Fair Value		930
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	331	797
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(4)	(3)
Total Fair Value	331	797
Total Unrealized Losses	(4)	(3)
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	1,017	2,594
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(12)	(6)
Continuous Unrealized Loss Position for 12 Months or Greater, Fair Value		136
Continuous Unrealized Loss Position for 12 Months or Greater, Unrealized Losses		(2)
Total Fair Value	1,017	2,730
Total Unrealized Losses	(12)	(8)
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	900	4,070
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses		(9)
Total Fair Value	900	4,070
Total Unrealized Losses		$ (9)
Foreign Government [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	75
Total Fair Value	$ 75

Restructuring - Schedule of Rec

Restructuring - Schedule of Reconciliation of Restructuring Liability (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Restructuring And Related Activities [Abstract]
Balance at beginning of period	$ 133		$ 1,568	$ 185	$ 185
Plus: Amounts charged to cost and expense	1,192	$ 1,400	1,745	$ 3,463	6,014
Less: Amounts paid	(967)		(2,955)		(4,631)
Balance at end of period	$ 358		$ 358		$ 1,568

Restructuring - Schedule of Com

Restructuring - Schedule of Components of Restructuring Expenses Including in Condensed Consolidated Statements of Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 1,192	$ 1,400	$ 1,745	$ 3,463	$ 6,014
Selling, General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	489	703	572	1,547
Research and Development Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	681	647	1,117	1,231
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 22	$ 50	$ 56	$ 685

Restructuring - Schedule of C_2

Restructuring - Schedule of Components of Restructuring Expense by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended		12 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Dec. 31, 2019
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 1,192	$ 1,400	$ 1,745	$ 3,463	$ 6,014
United States [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 1,192	541	1,743	825
International [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses		$ 859	$ 2	$ 2,638

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($) $ / shares in Units, $ in Millions	Aug. 05, 2020	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Sep. 03, 2020
Subsequent Event [Line Items]
Dividend payments		$ 0.09	$ 0.09	$ 0.09	$ 0.09
Scenario Forecast [Member]
Subsequent Event [Line Items]
Dividend declaration date	Aug. 5, 2020
Dividend payments	$ 0.09
Dividend record date	Aug. 20, 2020
Dividend payment date	Sep. 3, 2020
Quarterly dividend payable, aggregate amount subsequent to balance sheet date						$ 4.3