ADTRAN (ADTN) 10-Q 6 Nov 20 2020 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2020	Nov. 05, 2020
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2020
Document Fiscal Year Focus	2020
Document Fiscal Period Focus	Q3
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		47,956,220
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	Sep. 30, 2020	Dec. 31, 2019
Current Assets
Cash and cash equivalents	$ 71,081	$ 73,773
Restricted cash	322
Short-term investments	6,180	33,243
Accounts receivable, less allowance for doubtful accounts of $38 as of September 30, 2020 and December 31, 2019	100,223	90,531
Other receivables	22,899	16,566
Inventory	120,260	98,305
Prepaid expenses and other current assets	8,374	7,892
Total Current Assets	329,339	320,310
Property, plant and equipment, net	64,353	68,086
Deferred tax assets, net	7,865	7,561
Goodwill	6,968	6,968
Intangibles, net	24,465	27,821
Other assets	20,409	19,883
Long-term investments	78,016	94,489
Total Assets	531,415	545,118
Current Liabilities
Accounts payable	59,886	44,870
Bonds payable		24,600
Unearned revenue	13,379	11,963
Accrued expenses and other liabilities	13,173	13,876
Accrued wages and benefits	17,228	13,890
Income tax payable, net	3,346	3,512
Total Current Liabilities	107,012	112,711
Non-current unearned revenue	6,694	6,012
Pension liability	16,282	15,886
Deferred compensation liability	22,957	21,698
Other non-current liabilities	8,877	8,385
Total Liabilities	161,822	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 47,956 shares outstanding as of September 30, 2020 and 79,652 shares issued and 48,020 shares outstanding as of December 31, 2019	797	797
Additional paid-in capital	279,688	274,632
Accumulated other comprehensive loss	(12,678)	(16,417)
Retained earnings	788,294	806,702
Treasury stock at cost: 31,565 and 31,636 shares at September 30, 2020 and December 31, 2019, respectively	(686,508)	(685,288)
Total Stockholders’ Equity	369,593	380,426
Total Liabilities and Stockholders’ Equity	$ 531,415	$ 545,118

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 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	47,956,000	48,020,000
Treasury stock, shares	31,565,000	31,636,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Income (Loss) (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Sales
Total Sales	$ 133,143	$ 114,092	$ 376,381	$ 414,274
Cost of Sales
Total Cost of Sales	74,181	67,761	212,347	242,316
Gross Profit	58,962	46,331	164,034	171,958
Selling, general and administrative expenses	27,205	30,912	84,624	99,663
Research and development expenses	27,223	31,835	85,794	95,546
Asset impairments		3,872	65	3,872
Gain on contingency				(1,230)
Operating Income (Loss)	4,534	(20,288)	(6,449)	(25,893)
Interest and dividend income	344	610	1,031	1,893
Interest expense		(128)	(1)	(382)
Net investment gain (loss)	2,844	(216)	1,819	8,195
Other income (expense), net	(1,679)	1,616	(2,307)	2,266
Income (Loss) Before Income Taxes	6,043	(18,406)	(5,907)	(13,921)
Income tax (expense) benefit	(562)	(27,717)	2,171	(27,437)
Net Income (Loss)	$ 5,481	$ (46,123)	$ (3,736)	$ (41,358)
Weighted average shares outstanding – basic	47,957	47,824	47,957	47,803
Weighted average shares outstanding – diluted	48,424	47,824	47,957	47,803
Earnings (loss) per common share – basic	$ 0.11	$ (0.96)	$ (0.08)	$ (0.87)
Earnings (loss) per common share – diluted	$ 0.11	$ (0.96)	$ (0.08)	$ (0.87)
Network Solutions [Member]
Sales
Total Sales	$ 115,229	$ 94,018	$ 323,924	$ 359,007
Cost of Sales
Total Cost of Sales	62,795	56,444	178,492	207,353
Gross Profit	52,434	37,574	145,432	151,654
Services & Support [Member]
Sales
Total Sales	17,914	20,074	52,457	55,267
Cost of Sales
Total Cost of Sales	11,386	11,317	33,855	34,963
Gross Profit	$ 6,528	$ 8,757	$ 18,602	$ 20,304

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Statement Of Income And Comprehensive Income [Abstract]
Net Income (Loss)	$ 5,481	$ (46,123)	$ (3,736)	$ (41,358)
Other Comprehensive Income (Loss), net of tax
Net unrealized gains (losses) on available-for-sale securities	(45)	(15)	445	277
Defined benefit plan adjustments	244	90	576	361
Foreign currency translation	2,469	(2,486)	2,718	(3,113)
Other Comprehensive Income (Loss), net of tax	2,668	(2,411)	3,739	(2,475)
Comprehensive Income (Loss), net of tax	$ 8,149	$ (48,534)	$ 3	$ (43,833)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Cumulative Effect, Period of Adoption, Adjustment [Member]	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Retained Earnings [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]	Accumulated Other Comprehensive Loss [Member]Cumulative Effect, Period of Adoption, Adjustment [Member]
Beginning Balance at Dec. 31, 2018	$ 446,279	$ 4	$ 797	$ 267,670	$ 883,975	$ (381)	$ (691,747)	$ (14,416)	$ 385
Beginning Balance, Shares at Dec. 31, 2018			79,652
Net income (loss)	770				770
Other comprehensive income (loss), net of tax	(854)							(854)
Dividend payments ($0.09 per share)	(4,301)				(4,301)
Dividends accrued on unvested PSUs	(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	$ 4	$ 797	267,670	883,975	$ (381)	(691,747)	(14,416)	$ 385
Beginning Balance, Shares at Dec. 31, 2018			79,652
Net income (loss)	(41,358)
Other comprehensive income (loss), net of tax	(2,475)
Ending Balance at Sep. 30, 2019	394,955		$ 797	272,854	827,783		(689,973)	(16,506)
Ending Balance, Shares at Sep. 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 PSUs	(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
Net income (loss)	(46,123)				(46,123)
Other comprehensive income (loss), net of tax	(2,411)							(2,411)
Dividend payments ($0.09 per share)	(4,304)				(4,304)
Dividends accrued on unvested PSUs	42				42
PSUs, RSUs and restricted stock vested	(95)				(462)		367
Stock-based compensation expense	1,871			1,871
Ending Balance at Sep. 30, 2019	394,955		$ 797	272,854	827,783		(689,973)	(16,506)
Ending Balance, Shares at Sep. 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 PSUs	(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)	$ (3,736)
Other comprehensive income (loss), net of tax	3,739
Ending Balance at Sep. 30, 2020	$ 369,593		$ 797	279,688	788,294		(686,508)	(12,678)
Ending Balance, Shares at Sep. 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 PSUs	(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
Net income (loss)	5,481				5,481
Other comprehensive income (loss), net of tax	2,668							2,668
Dividend payments ($0.09 per share)	(4,328)				(4,328)
Dividends accrued on unvested PSUs	(12)				(12)
Deferred compensation adjustments, net of tax	(12)						(12)
PSUs, RSUs and restricted stock vested	(8)				(67)		59
Stock-based compensation expense	1,610			1,610
Ending Balance at Sep. 30, 2020	$ 369,593		$ 797	$ 279,688	$ 788,294		$ (686,508)	$ (12,678)
Ending Balance, Shares at Sep. 30, 2020	79,652		79,652

Condensed Consolidated Statem_4

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

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019
Cash flows from operating activities:
Net loss	$ (3,736)	$ (41,358)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation and amortization	12,525	13,315
Asset impairments	65	3,872
Amortization of net premium on available-for-sale investments	90	(86)
Net gain on long-term investments	(1,819)	(8,195)
Net loss on disposal of property, plant and equipment	105	58
Gain on contingency		(1,230)
Gain on life insurance proceeds		(1,000)
Stock-based compensation expense	5,056	5,184
Deferred income taxes	(1)	30,421
Changes in operating assets and liabilities:
Accounts receivable, net	(9,131)	7,603
Other receivables	(6,224)	17,645
Inventory	(21,170)	(5,998)
Prepaid expenses and other assets	(672)	(10,071)
Accounts payable, net	14,204	(5,569)
Accrued expenses and other liabilities	5,618	10,564
Income taxes payable	(227)	(5,073)
Net cash provided by (used in) operating activities	(5,317)	10,082
Cash flows from investing activities:
Purchases of property, plant and equipment	(5,082)	(6,008)
Proceeds from sales and maturities of available-for-sale investments	86,145	38,561
Purchases of available-for-sale investments	(42,641)	(37,223)
Acquisition of note receivable	(523)
Life insurance proceeds received		1,000
Acquisition of business		13
Net cash provided by (used in) investing activities	37,899	(3,657)
Cash flows from financing activities:
Dividend payments	(12,993)	(12,908)
Repayment of bonds payable	(24,600)
Proceeds from stock option exercises		526
Purchases of treasury stock		(184)
Net cash used in financing activities	(37,593)	(12,566)
Net decrease in cash, cash equivalents and restricted cash	(5,011)	(6,141)
Effect of exchange rate changes	2,641	(2,956)
Cash, cash equivalents and restricted cash, beginning of period	73,773	105,504
Cash, cash equivalents and restricted cash, end of period	71,403	96,407
Supplemental disclosure of non-cash investing activities:
Purchases of property, plant and equipment included in accounts payable	$ 442	$ 135

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 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 September 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, excess and obsolete inventory reserves, 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 condensed consolidated financial statements as of and for the three and nine month periods ended September 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 nine months ended September 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 September 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 There was no impact upon adoption of ASU 2018-15 on the Condensed Consolidated Statement of Loss for the three and nine months ended September 30, 2019 and the Condensed Consolidated Statement of Cash Flows for nine months ended September 30, 2019 as outlined in the following tables: Three months ended September 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Loss Net loss $ (46,123 ) $ — $ (46,123 ) Nine months ended September 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Loss Net loss $ (41,358 ) $ — $ (41,358 ) Condensed Consolidated Statement of Cash Flows Net cash provided by operating activities $ 10,082 $ — $ 10,082 The following table presents the capitalized implementation costs incurred with hosting arrangements, included in other assets on the Condensed Consolidated Balance Sheet, as of September 30, 2020: (In thousands) September 30, 2020 Implementation costs - hosting arrangements $ 10,455 Less: accumulated amortization — Implementation costs - hosting arrangements, net $ 10,455 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	9 Months Ended
	Sep. 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 Condensed Consolidated Balance Sheet that sum to the total of the same such amounts shown in the Condensed Consolidated Statement of Cash Flows: (In thousands) September 30, 2020 Cash and cash equivalents $ 71,081 Restricted cash 322 Cash, cash equivalents and restricted cash $ 71,403 The Company did not have any restricted cash as of December 31, 2019. See Note 18 for additional information regarding restricted cash.

Revenue

Revenue	9 Months Ended
	Sep. 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 - 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 - 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 nine months ended September 30, 2020 and 2019: Three Months Ended September 30, 2020 September 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 71,919 $ 13,504 $ 85,423 $ 48,902 $ 16,212 $ 65,114 Subscriber Solutions & Experience 40,843 2,282 43,125 40,382 2,094 42,476 Traditional & Other Products 2,467 2,128 4,595 4,734 1,768 6,502 Total $ 115,229 $ 17,914 $ 133,143 $ 94,018 $ 20,074 $ 114,092 Nine Months Ended September 30, 2020 September 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 194,695 $ 39,470 $ 234,165 $ 230,837 $ 43,476 $ 274,313 Subscriber Solutions & Experience 118,907 6,790 125,697 113,545 6,186 119,731 Traditional & Other Products 10,322 6,197 16,519 14,625 5,605 20,230 Total $ 323,924 $ 52,457 $ 376,381 $ 359,007 $ 55,267 $ 414,274 Revenue allocated to remaining performance obligations represents contract revenue that have not yet been recognized for contracts with a duration of greater than one year. As of September 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 $16.5 million and $13.6 million as of September 30, 2020 and December 31, 2019, respectively. The Company expects to recognize 59% of the $16.5 million as of September 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) September 30, 2020 December 31, 2019 Accounts receivable, net $ 100,223 $ 90,531 Contract assets (1) $ 1,015 $ 2,812 Unearned revenue $ 13,379 $ 11,963 Non-current unearned revenue $ 6,694 $ 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, $1.5 million and $1.2 million were recognized as revenue during the three months ended September 30, 2020 and 2019 and $9.6 million and $11.7 million were recognized as revenue during the nine months ended September 30, 2020 and 2019, respectively.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2020
Income Tax Disclosure [Abstract]
Income Taxes	4. INCOME TAXES Our effective tax rate decreased from an expense of 150.6% for the three months ended September 30, 2019 to an expense of 9.3% for the three months ended September 30, 2020 and decreased from an expense of 197.1% for the nine months ended September 30, 2019 to a benefit of 36.8% for the nine months ended September 30, 2020. The change in the effective tax rate for the three months ended September 30, 2020 was impacted by tax expense in our international operations, offset by additional changes in the valuation allowance related to our domestic operations of $1.0 million and by additional benefits recognized during the quarter of $0.4 million as a result of the Coronavirus Aid, Relief, and Economic Security (“CARES”) Act signed into law on March 27, 2020 in conjunction with the Internal Revenue Service’s release of its final Global Intangible Low Tax Income (“GILTI”) regulations on July 9th, 2020. The change in the effective tax rate for the three and nine months ended September 30, 2019 was primarily driven by the establishment of the valuation allowance against our domestic deferred tax assets in the amount of $37.1 7.1% was primarily driven by a tax benefit of $7.8 million recognized during the nine months ended September 30, 2020 as a result of the CARES Act, 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 $2.6 million during the nine months ended September 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 September 30, 2020 and December 31, 2019 is as follows: September 30, 2020 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 49,212 $ (49,212 ) $ — International 9,892 (2,027 ) 7,865 Total $ 59,104 $ (51,239 ) $ 7,865 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	9 Months Ended
	Sep. 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 nine months ended September 30, 2020 and 2019: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Service cost $ 325 $ 366 $ 942 $ 1,109 Interest cost 113 158 329 479 Expected return on plan assets (429 ) (346 ) (1,246 ) (1,049 ) Amortization of actuarial losses 248 198 720 600 Net periodic pension cost $ 257 $ 376 $ 745 $ 1,139 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	9 Months Ended
	Sep. 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 nine months ended September 30, 2020 and 2019: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Stock-based compensation expense included in cost of sales $ 101 $ 83 $ 303 $ 272 Selling, general and administrative expense 953 1,142 2,999 2,867 Research and development expense 556 646 1,754 2,045 Stock-based compensation expense included in operating expenses 1,509 1,788 4,753 4,912 Total stock-based compensation expense 1,610 1,871 5,056 5,184 Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock (384 ) (446 ) (1,205 ) (1,235 ) Total stock-based compensation expense, net of tax $ 1,226 $ 1,425 $ 3,851 $ 3,949 PSUs, RSUs and Restricted Stock The following table summarizes PSUs, RSUs and restricted stock outstanding as of December 31, 2019 and September 30, 2020 and the changes that occurred during the nine months ended September 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 (15 ) $ 12.76 PSUs, RSUs and restricted stock forfeited (586 ) $ 18.24 Unvested PSUs, RSUs and restricted stock outstanding, September 30, 2020 1,689 $ 11.83 During the nine months ended September 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 a 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 September 30, 2020, total unrecognized compensation expense related to unvested market-based PSUs, RSUs and restricted stock was approximately $10.6 million, which will be recognized over the remaining weighted-average period of 2.3 years. In addition, there was $2.3 million of unrecognized compensation expense related to unvested 2020 performance-based PSUs, which will be recognized over the remaining requisite service period of 2.3 years if achievement of the performance obligation becomes probable. 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. Stock options, RSUs and restricted stock granted under the 2020 Employee Plan reduce the shares authorized for issuance under the 2020 Employee Plan by one 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 stock options from the 2015 Employee Plan increase the shares authorized for issuance under the 2020 Employee Plan by one 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 through stock options, restricted stock and RSUs to 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. Stock options issued under the 2020 Directors Plan will have a ten-year As of September 30, 2020, 3.6 million shares, including forfeitures to date under the 2015 Employee Plan and the 2010 Directors Stock Plan, were available for issuance under stockholder-approved equity plans. Stock Options The following table summarizes stock options outstanding as of December 31, 2019 and September 30, 2020 and the changes that occurred during the nine months ended September 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 (352 ) $ 21.48 Stock options outstanding, September 30, 2020 3,220 $ 22.94 2.7 $ — Stock options exercisable, September 30, 2020 3,217 $ 22.95 2.7 $ — As of September 30, 2020, total unrecognized compensation expense related to unvested stock options was approximately $1 thousand, which will be recognized over the remaining weighted-average period of 0.1 years. Unrecognized compensation expense will be adjusted for actual forfeitures. There were no stock options granted during the three and nine months ended September 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 September 30, 2020. The amount of aggregate intrinsic value will change based on the fair market value of the Company’s stock and was zero as of September 30, 2020. The total pre-tax intrinsic value of options exercised during the nine months ended September 30, 2020 was zero.

Investments

Investments	9 Months Ended
	Sep. 30, 2020
Investments Debt And Equity Securities [Abstract]
Investments	7. INVESTMENTS Debt Securities and Other Investments As of September 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 $ 12,861 $ 149 $ — $ 13,010 Municipal fixed-rate bonds 3,093 32 (1 ) 3,124 Asset-backed bonds 8,472 115 — 8,587 Mortgage/Agency-backed bonds 10,964 127 (11 ) 11,080 U.S. government bonds 7,096 174 — 7,270 Foreign government bonds 1,032 3 — 1,035 Commercial paper 324 1 — 325 Variable-rate demand notes — — — — Other 442 — — 442 Available-for-sale debt securities held at fair value $ 44,284 $ 601 $ (12 ) $ 44,873 As 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 September 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 Other Less than one year $ 2,900 $ 737 $ 696 $ 208 $ 500 $ 75 $ 325 $ 442 One to two years 3,752 1,183 956 1,256 826 463 — — Two to three years 6,122 908 615 2,775 5,492 497 — — Three to five years 236 296 4,817 1,079 452 — — — Five to ten years — — 946 1,507 — — — — More than ten years — — 557 4,255 — — — — Total $ 13,010 $ 3,124 $ 8,587 $ 11,080 $ 7,270 $ 1,035 $ 325 $ 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 Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Gross realized gains on debt securities $ 70 $ 36 $ 303 $ 85 Gross realized losses on debt securities (6 ) (7 ) (45 ) (40 ) Total gain recognized, net $ 64 $ 29 $ 258 $ 45 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 the total investment portfolio. The Company did not purchase any available-for-sale debt security with credit deterioration during the three and nine months ended September 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 nine months ended September 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 September 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 September 30, 2020 and December 31, 2019, and represented a non-cash investing activity during the nine months ended September 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 nine months ended September 30, 2020 and 2019 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Realized gains (losses) on equity securities sold $ 623 $ (20 ) $ (1,485 ) $ (83 ) Unrealized gains (losses) on equity securities held 2,157 (225 ) 3,046 8,233 Total gain (loss) recognized, net $ 2,780 $ (245 ) $ 1,561 $ 8,150 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; 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 September 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 $ 636 $ 636 $ — $ — U.S. government securities 300 300 — — Available-for-sale debt securities Corporate bonds 13,010 — 13,010 — Municipal fixed-rate bonds 3,124 — 3,124 — Asset-backed bonds 8,587 — 8,587 — Mortgage/Agency-backed bonds 11,080 — 11,080 — U.S. government bonds 7,270 7,270 — — Foreign government securities 1,035 — 1,035 — Commercial paper 325 — 325 — Variable-rate demand notes — — — Other 442 — — 442 Marketable equity securities Marketable equity securities – various industries 13,590 13,590 — — Deferred compensation plan assets 21,595 21,595 — — Other investments 1,276 1,276 — — Total $ 82,270 $ 44,667 $ 37,161 $ 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	9 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Inventory	8. INVENTORY As of September 30, 2020 and December 31, 2019, inventory consisted of the following: September 30, December 31, (In thousands) 2020 2019 Raw materials $ 43,418 $ 36,987 Work in process 1,787 1,085 Finished goods 75,055 60,233 Total inventory $ 120,260 $ 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 September 30, 2020 and December 31, 2019, inventory reserves were $38.0 million and $34.1 million, respectively

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	9. PROPERTY, PLANT AND EQUIPMENT At September 30, 2020 and December 31, 2019, property, plant and equipment consisted of the following: September 30, December 31, (In thousands) 2020 2019 Land $ 4,575 $ 4,575 Building and land improvements 35,105 34,797 Building 68,160 68,157 Furniture and fixtures 19,981 19,959 Computer hardware and software 70,766 68,777 Engineering and other equipment 132,672 130,430 Total property, plant and equipment 331,259 326,695 Less: accumulated depreciation (266,906 ) (258,609 ) Total property, plant and equipment, net $ 64,353 $ 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 third 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 $3.1 million for both the three months ended September 30, 2020 and 2019, and $9.1 million and $9.3 million for the nine months ended September 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	9 Months Ended
	Sep. 30, 2020
Goodwill Disclosure [Abstract]
Goodwill	10. GOODWILL Goodwill was $7.0 million as of September 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. Qualitative factors are assessed 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, if applicable. 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 September 30, 2020, and no impairment of goodwill was recorded during the three and nine months ended September 30, 2020.

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2020
Intangible Assets Net Excluding Goodwill [Abstract]
Intangible Assets	11. Intangible assets as of September 30, 2020 and December 31, 2019 consisted of the following: September 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 $ 20,931 $ (7,369 ) $ 13,562 $ 22,356 $ (7,233 ) $ 15,123 Developed technology 8,200 (2,262 ) 5,938 10,170 (3,379 ) 6,791 Licensed technology 5,900 (1,666 ) 4,234 5,900 (1,174 ) 4,726 Supplier relationships 2,800 (2,800 ) — 2,800 (2,508 ) 292 Licensing agreements 560 (134 ) 426 560 (79 ) 481 Patents 500 (277 ) 223 500 (226 ) 274 Trade names 210 (128 ) 82 310 (176 ) 134 Total $ 39,101 $ (14,636 ) $ 24,465 $ 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 third quarter of 2020. Based on this assessment, no triggers occurred to perform an impairment test, and no impairment losses of intangible assets were recorded during the three and nine months ended September 30, 2020. Amortization expense was $1.0 million and $1.3 million for the three months ended September 30, 2020 and 2019, respectively, and $3.4 million and $4.0 million for the nine months ended September 30, 2020 and 2019, respectively, and was included in cost of sales, selling, general and administrative expenses and research and development expenses As of September 30, 2020, estimated future amortization expense of intangible assets was as follows: (In thousands) 2020 $ 1,041 2021 4,107 2022 3,482 2023 3,330 2024 3,236 Thereafter 9,269 Total $ 24,465

Leases

Leases	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Leases	12. LEASES Operating Leases The Company’s o perating 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 September 30, 2020, the Company’s 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 . As of September 30, 2020 and December 31, 2019, the Company’s operating lease assets and operating lease liabilities were as follows: (In thousands) Classification September 30, 2020 December 31, 2019 Assets Operating lease asset Other assets $ 5,503 $ 8,452 Total lease asset $ 5,503 $ 8,452 Liabilities Current operating lease liability Accrued expenses $ 1,731 $ 2,676 Non-current operating lease liability Other non-current liabilities 3,788 5,818 Total lease liability $ 5,519 $ 8,494 Lease expense related to short-term leases (initial term of less than 12 months) was $6 thousand and $0.1 million for the three months ended September 30, 2020 and 2019, respectively, and was $20 thousand and $0.3 million for the nine months ended September 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 September 30, 2020 and 2019, respectively and was $0.4 million and $0.7 million for the nine months ended September 30, 2020 and 2019, respectively. Components of lease expense included in the Condensed Consolidated Statements of Income (Loss) for the three and nine months ended September 30, 2020 and 2019 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Cost of sales $ 21 $ 16 $ 68 $ 49 Selling, general and administrative expenses 265 352 863 1,050 Research and development expenses 368 847 1,044 1,731 Total operating lease expense $ 654 $ 1,215 $ 1,975 $ 2,830 As of September 30, 2020 and December 31, 2019, operating lease liabilities included on the Condensed Consolidated Balance Sheets by future maturity were as follows: (In thousands) September 30, 2020 December 31, 2019 2020 $ 518 $ 2,856 2021 1,744 2,412 2022 1,514 1,705 2023 1,180 1,160 2024 499 482 Thereafter 276 264 Total lease payments 5,731 8,879 Less: Interest (212 ) (385 ) Present value of lease liabilities $ 5,519 $ 8,494 Future o perating lease payments include $0.3 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 September 30, 2020 and December 31, 2019 : As of September 30, 2020 As of December 31, 2019 Weighted average remaining lease term (in years) Operating leases with USD functional currency 2.6 2.6 Operating leases with Euro functional currency 3.8 4.4 Weighted average discount rate Operating leases with USD functional currency 4.50 % 4.02 % Operating leases with Euro functional currency 1.81 % 1.84 % Supplemental cash flow information related to operating leases is as follows: Three Months Ended Nine Months Ended September 30, September 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 $ 582 $ 775 $ 2,059 $ 2,383 Right-of-use assets obtained in exchange for lease obligations $ 138 $ 11,022 $ 231 $ 21,418 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 September 30, 2020 and December 31, 2019: (In thousands) September 30, 2020 December 31, 2019 Current minimum lease payments receivable (1) $ 811 $ 1,201 Non-current minimum lease payments receivable (2) 450 889 Total minimum lease payments receivable 1,261 2,090 Less: Current unearned revenue 235 365 Less: Non-current unearned revenue 70 163 Net investment in sales-type leases $ 956 $ 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 nine months ended September 30, 2020 and 2019 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Sales - Network Solutions $ 22 $ 47 $ 72 $ 1,668 Less: Cost of sales - Network Solutions 9 25 29 660 Gross profit $ 13 $ 22 $ 43 $ 1,008 Interest and dividend income $ 10 $ 92 $ 34 $ 278

Alabama State Industrial Develo

Alabama State Industrial Development Authority Financing and Economic Incentives	9 Months Ended
	Sep. 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	9 Months Ended
	Sep. 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 nine months ended September 30, 2020, we did not repurchase shares of our common stock. As of September 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 income (loss), net of tax, by component for the three months ended September 30, 2020 and 2019: Three Months Ended September 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 June 30, 2020 $ 206 $ (8,894 ) $ (7,043 ) $ 385 $ (15,346 ) Other comprehensive income before reclassifications 494 — 2,469 — 2,963 Amounts reclassified from accumulated other comprehensive income (loss) (539 ) 244 — — (295 ) Net current period other comprehensive income (45 ) 244 2,469 — 2,668 As of September 30, 2020 $ 161 $ (8,650 ) $ (4,574 ) $ 385 $ (12,678 ) Three Months Ended September 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 June 30, 2019 $ (271 ) $ (7,770 ) $ (6,439 ) $ 385 $ (14,095 ) Other comprehensive income before reclassifications (39 ) — (2,486 ) — (2,525 ) Amounts reclassified from accumulated other comprehensive income (loss) 24 90 — — 114 Net current period other comprehensive income (15 ) 90 (2,486 ) — (2,411 ) As of September 30, 2019 $ (286 ) $ (7,680 ) $ (8,925 ) $ 385 $ (16,506 ) (1) The following tables present the changes in accumulated other comprehensive income ( loss ) , net of tax , by component for the nine months ended September 30, 2020 and 2019 : Nine Months Ended September 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 444 — 2,718 — 3,162 Amounts reclassified from accumulated other comprehensive income 1 576 — — 577 Net current period other comprehensive income 445 576 2,718 — 3,739 As of September 30, 2020 $ 161 $ (8,650 ) $ (4,574 ) $ 385 $ (12,678 ) Nine Months Ended September 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 372 — (3,113 ) — (2,741 ) Amounts reclassified from accumulated other comprehensive income (loss) (95 ) 361 — — 266 Amounts reclassified to retained earnings (1) — — — 385 385 Net current period other comprehensive income (loss) 277 361 (3,113 ) 385 (2,090 ) As of September 30, 2019 $ (286 ) $ (7,680 ) $ (8,925 ) $ 385 $ (16,506 ) (1) The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the three months ended September 30, 2020 and 2019: Three Months Ended September 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 $ 728 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (354 ) (1) Total reclassifications for the period, before tax 374 Tax expense (79 ) Total reclassifications for the period, net of tax $ 295 (1) Three Months Ended September 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 losses on sales of securities $ (32 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (130 ) (1) Total reclassifications for the period, before tax (162 ) Tax benefit 48 Total reclassifications for the period, net of tax $ (114 ) (1) The following tables present the details of reclassifications out of accumulated other comprehensive loss for the nine months ended September 30, 2020 and 2019: Nine Months Ended September 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 $ (1 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (835 ) (1) Total reclassifications for the period, before tax (836 ) Tax benefit 259 Total reclassifications for the period, net of tax $ (577 ) (1) Nine Months Ended September 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 on available-for-sale securities: Net realized gains on sales of securities $ 128 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (523 ) (1) Total reclassifications for the period, before tax (395 ) Tax benefit 129 Total reclassifications for the period, net of tax $ (266 ) (1) The following table presents the tax effects related to the change in each component of other comprehensive loss for the three months ended September 30, 2020 and 2019: Three Months Ended Three Months Ended September 30, 2020 September 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 $ 668 $ (174 ) $ 494 $ (53 ) $ 14 $ (39 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss) (728 ) 189 (539 ) 32 (8 ) 24 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss) 354 (110 ) 244 130 (40 ) 90 Foreign currency translation adjustment 2,469 — 2,469 (2,486 ) — (2,486 ) Total Other Comprehensive Income (Loss) $ 2,763 $ (95 ) $ 2,668 $ (2,377 ) $ (34 ) $ (2,411 ) The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the nine months ended September 30, 2020 and 2019: Nine Months Ended Nine Months Ended September 30, 2020 September 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 $ 600 $ (156 ) $ 444 $ 503 $ (131 ) $ 372 Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss) 1 — 1 (128 ) 33 (95 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss) 835 (259 ) 576 523 (162 ) 361 Foreign currency translation adjustment 2,718 — 2,718 (3,113 ) — (3,113 ) Total Other Comprehensive Income (Loss) $ 4,154 $ (415 ) $ 3,739 $ (2,215 ) $ (260 ) $ (2,475 )

Earnings (Loss) Per Share

Earnings (Loss) Per Share	9 Months Ended
	Sep. 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 nine months ended September 30, 2020 and 2019 is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share amounts) 2020 2019 2020 2019 Numerator Net income (loss) $ 5,481 $ (46,123 ) $ (3,736 ) $ (41,358 ) Denominator Weighted average number of shares – basic 47,957 47,824 47,957 47,803 Effect of dilutive securities PSUs, RSUs and restricted stock 467 — — — Weighted average number of shares – diluted 48,424 47,824 47,957 47,803 Earnings (loss) per share – basic $ 0.11 $ (0.96 ) $ (0.08 ) $ (0.87 ) Earnings (loss) per share – diluted $ 0.11 $ (0.96 ) $ (0.08 ) $ (0.87 ) For the three months ended September 30, 2020 and 2019, 18 thousand and 0.1 million shares, respectively, and for the nine months ended September 30, 2020 and 2019, 0.1 million shares, of unvested or unearned, as applicable, 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 September 30, 2020 and 2019, 3.4 million and 3.9 million stock options, respectively, and for the nine months ended September 30, 2020 and 2019, 4.3 million and 2.8 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	9 Months Ended
	Sep. 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 products and software defined 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 implementation and solutions integration and managed 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 income tax (expense) benefit 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 nine months ended September 30, 2020 and 2019. Three Months Ended September 30, 2020 September 30, 2019 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 115,229 $ 52,434 $ 94,018 $ 37,574 Services & Support 17,914 6,528 20,074 8,757 Total $ 133,143 $ 58,962 $ 114,092 $ 46,331 Nine Months Ended September 30, 2020 September 30, 2019 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 323,924 $ 145,432 $ 359,007 $ 151,654 Services & Support 52,457 18,602 55,267 20,304 Total $ 376,381 $ 164,034 $ 414,274 $ 171,958 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 table below presents sales information by category for the three and nine months ended September 30, 2020 and 2019: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Access & Aggregation $ 85,423 $ 65,114 $ 234,165 $ 274,313 Subscriber Solutions & Experience 43,125 42,476 125,697 119,731 Traditional & Other Products 4,595 6,502 16,519 20,230 Total $ 133,143 $ 114,092 $ 376,381 $ 414,274 Sales by Geographic Area The following table presents sales information by geographic area for the three and nine months ended September 30, 2020 and 2019: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 United States $ 92,838 $ 83,144 $ 256,287 $ 230,960 International 40,305 30,948 120,094 183,314 Total $ 133,143 $ 114,092 $ 376,381 $ 414,274

Liability for Warranty Returns

Liability for Warranty Returns	9 Months Ended
	Sep. 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 $7.2 million and $8.4 million as of September 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 nine months ended September 30, 2020 and 2019 is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Balance at beginning of period $ 7,294 $ 8,972 $ 8,394 $ 8,623 Plus: Amounts charged to cost and expenses 632 816 970 3,796 Less: Deductions (734 ) (1,131 ) (2,172 ) (3,762 ) Balance at end of period $ 7,192 $ 8,657 $ 7,192 $ 8,657

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 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 September 30, 2020 and December 31, 2019, we had commitments related to these bonds totaling $12.0 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 2020, the Company entered into a letter of credit with a bank to guarantee performance obligations under a contract with a certain customer. The obligations under the customer contract will be performed over multiple years. As of September 30, 2020, the Company was required to maintain a minimum collateral value of $4.5 million. The letter of credit was secured by a pledge of a portion of the Company’s fixed-income securities, which totaled $5.9 million as of September 30, 2020, of which $0.3 million is included in restricted cash and $5.6 million is included in long-term investments on the Condensed Consolidated Balance Sheet. This pledged collateral value will fluctuate as the Company changes the mix of the pledged collateral between restricted cash and investments, with an expected maximum value between $13.0 million and $15.0 million. On October 8, 2020, the Company entered into an amendment to the letter of credit, which increased the minimum collateral value to $9.0 million. The minimum collateral value is expected to continue to increase as the Company reaches certain milestones through the first quarter of 2021 as outlined in the customer contract. Any shortfalls in the minimum collateral value are required to be restored by the Company from available cash and cash equivalents, short-term investments and/or long-term investments. The collateral under the letter of credit will be released when all obligations under the customer contract have been met. As of September 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 September 30, 2020.

Current Expected Credit Losses

Current Expected Credit Losses	9 Months Ended
	Sep. 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 September 30, 2020, the Company’s outstanding accounts receivable balance was $90.5 million and $100.2 million, respectively. The Company assessed the need for an allowance for credit losses related to its outstanding accounts receivable as of September 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 nine months ended September 30, 2020 related to accounts receivable. The Company’s allowance for credit losses related to accounts receivable was $38 thousand as of September 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 September 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 September 30, 2020. The Company assessed the need for an allowance for credit losses related to its outstanding contract assets as of September 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 nine months ended September 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 September 30, 2020, the Company’s outstanding net investment in sales-type leases was $1.6 million and $1.0 million, respectively, which is included in other receivables and other assets on the Condensed Consolidated Balance Sheets as of December 31, 2019 and September 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 September 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 $ 58 $ 227 $ 426 $ 153 $ 89 $ 3 $ 956 Non-performing — — — — — — — Total $ 58 $ 227 $ 426 $ 153 $ 89 $ 3 $ 956 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 nine months ended September 30, 2020 related to sales-type leases. Secured Loan Receivable The Company has a secured loan receivable totaling $0.9 million as of January 1, 2020 and September 30, 2020, which originated in February 2019, and is included in long-term investments on the Condensed Consolidated Balance Sheets as of September 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 September 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 September 30, 2020 and December 31, 2019, totaled $24 thousand and $0 as of January 1, 2020 and September 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 nine months ended September 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 September 30, 2020. As of January 1, 2020 and September 30, 2020, the Company’s available-for-sale debt securities totaled $37.7 million and $44.9 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 September 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 September 30, 2020. The Company had 45 positions in available-for-sale debt securities that were in an unrealized loss position as of September 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 — — — — — — Municipal fixed-rate bonds 394 (1 ) — — 394 (1 ) Asset-backed bonds 396 — — — 396 — Mortgage/Agency-backed bonds 3,199 (11 ) — — 3,199 (11 ) U.S. government bonds 800 — — — 800 — Foreign government bonds 75 — — — 75 — Total $ 4,864 $ (12 ) $ — $ — $ 4,864 $ (12 ) 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 ) Foreign government bonds 371 (1 ) — — 371 (1 ) Total $ 8,965 $ (19 ) $ 136 $ (2 ) $ 9,101 $ (21 ) 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 nine months ended September 30, 2020 related to the Company’s available-for-sale debt securities.

Restructuring

Restructuring	9 Months Ended
	Sep. 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 and was announced in March 2019 and again in August 2020. A reconciliation of the beginning and ending restructuring liability, which is included in accrued wages and benefits on the Condensed Consolidated Balance Sheets as of September 30, 2020 and December 31, 2019, is as follows: Three Months Ended Nine Months Ended (In thousands) September 30, 2020 September 30, 2020 Balance at beginning of period $ 358 $ 1,568 Plus: Amounts charged to expense 1,903 3,648 Less: Amounts paid (542 ) (3,497 ) Balance as of September 30, 2020 $ 1,719 $ 1,719 (In thousands) December 31, 2019 Balance as of December 31, 2018 $ 185 Plus: Amounts charged to 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 Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Cost of sales 232 62 288 747 Selling, general and administrative expenses $ 1,050 $ 531 $ 1,622 $ 2,078 Research and development expenses 621 602 1,738 1,833 Total restructuring expenses $ 1,903 $ 1,195 $ 3,648 $ 4,658 The following table represents the components of restructuring expenses by geographic area: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Domestic $ 448 $ 1,116 $ 2,191 $ 1,941 International 1,455 79 1,457 2,717 Total restructuring expenses $ 1,903 $ 1,195 $ 3,648 $ 4,658 The cumulative amount of restructuring expenses incurred as of September 30, 2020 for the restructuring plans announced in 2019 and 2020 was $9.7 million.

Subsequent Events

Subsequent Events	9 Months Ended
	Sep. 30, 2020
Subsequent Events [Abstract]
Subsequent Events	21. SUBSEQUENT EVENTS On November 2, 2020, the Company announced that its 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 November 17, 2020. The payment date will be December 1, 2020 in the aggregate amount of approximately $4.3 million. On November 4, 2020, the Company, as borrower, entered into a Revolving Credit and Security Agreement and related Promissory Note (together, the “Revolving Credit Agreement”) with Cadence Bank, N.A., as lender (the “Lender”). The Revolving Credit Agreement provides the Company with a new $10 million secured revolving credit facility. Loans under the Revolving Credit Agreement will bear interest at a rate equal to 1.50% over the screen rate as obtained by Reuter’s, Bloomberg or another commercially available source as may be designated by the Lender from time to time; provided, however, that in no event shall the applicable rate of interest under the Revolving Credit Agreement be less than 1.50% per annum. Such loans are secured by all of the cash, securities, securities entitlements and investment property in a certain bank account, as outlined in the Revolving Credit Agreement, at a maximum loan-to-value ratio of 75% determined by dividing the full commitment amount under the Revolving Credit Agreement on the date of testing, determined by the Lender each fiscal quarter, by the market value of the collateral. The Revolving Credit Agreement matures on November 4, 2021, subject to earlier termination upon the occurrence of certain events of default. The Company has not made any draws under the Revolving Credit Agreement to date.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 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 September 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, excess and obsolete inventory reserves, 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 condensed consolidated financial statements as of and for the three and nine month periods ended September 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 nine months ended September 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 September 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 There was no impact upon adoption of ASU 2018-15 on the Condensed Consolidated Statement of Loss for the three and nine months ended September 30, 2019 and the Condensed Consolidated Statement of Cash Flows for nine months ended September 30, 2019 as outlined in the following tables: Three months ended September 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Loss Net loss $ (46,123 ) $ — $ (46,123 ) Nine months ended September 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Loss Net loss $ (41,358 ) $ — $ (41,358 ) Condensed Consolidated Statement of Cash Flows Net cash provided by operating activities $ 10,082 $ — $ 10,082 The following table presents the capitalized implementation costs incurred with hosting arrangements, included in other assets on the Condensed Consolidated Balance Sheet, as of September 30, 2020: (In thousands) September 30, 2020 Implementation costs - hosting arrangements $ 10,455 Less: accumulated amortization — Implementation costs - hosting arrangements, net $ 10,455 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)	9 Months Ended
	Sep. 30, 2020
Schedule of Capitalized Implementation Costs Incurred with Hosting Arrangements, Included in Other Assets on Condensed Consolidated Balance Sheet	The following table presents the capitalized implementation costs incurred with hosting arrangements, included in other assets on the Condensed Consolidated Balance Sheet, as of September 30, 2020: (In thousands) September 30, 2020 Implementation costs - hosting arrangements $ 10,455 Less: accumulated amortization — Implementation costs - hosting arrangements, net $ 10,455
ASU 2018-15 [Member]
Schedule of Impact of Adoption of ASU 2018-15 on Condensed Consolidated Balance Sheet, Statement of Loss 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 There was no impact upon adoption of ASU 2018-15 on the Condensed Consolidated Statement of Loss for the three and nine months ended September 30, 2019 and the Condensed Consolidated Statement of Cash Flows for nine months ended September 30, 2019 as outlined in the following tables: Three months ended September 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Loss Net loss $ (46,123 ) $ — $ (46,123 ) Nine months ended September 30, 2019 (In thousands) Pre-Adoption Effect of Adoption As Presented Now Condensed Consolidated Statement of Loss Net loss $ (41,358 ) $ — $ (41,358 ) Condensed Consolidated Statement of Cash Flows Net cash provided by operating activities $ 10,082 $ — $ 10,082

Cash, Cash Equivalents and Re_2

Cash, Cash Equivalents and Restricted Cash (Tables)	9 Months Ended
	Sep. 30, 2020
Cash And Cash Equivalents [Abstract]
Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash	The following table provides a reconciliation of cash, cash equivalents and restricted cash reported within the Condensed Consolidated Balance Sheet that sum to the total of the same such amounts shown in the Condensed Consolidated Statement of Cash Flows: (In thousands) September 30, 2020 Cash and cash equivalents $ 71,081 Restricted cash 322 Cash, cash equivalents and restricted cash $ 71,403

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 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 nine months ended September 30, 2020 and 2019: Three Months Ended September 30, 2020 September 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 71,919 $ 13,504 $ 85,423 $ 48,902 $ 16,212 $ 65,114 Subscriber Solutions & Experience 40,843 2,282 43,125 40,382 2,094 42,476 Traditional & Other Products 2,467 2,128 4,595 4,734 1,768 6,502 Total $ 115,229 $ 17,914 $ 133,143 $ 94,018 $ 20,074 $ 114,092 Nine Months Ended September 30, 2020 September 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 194,695 $ 39,470 $ 234,165 $ 230,837 $ 43,476 $ 274,313 Subscriber Solutions & Experience 118,907 6,790 125,697 113,545 6,186 119,731 Traditional & Other Products 10,322 6,197 16,519 14,625 5,605 20,230 Total $ 323,924 $ 52,457 $ 376,381 $ 359,007 $ 55,267 $ 414,274 The table below presents sales information by category for the three and nine months ended September 30, 2020 and 2019: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Access & Aggregation $ 85,423 $ 65,114 $ 234,165 $ 274,313 Subscriber Solutions & Experience 43,125 42,476 125,697 119,731 Traditional & Other Products 4,595 6,502 16,519 20,230 Total $ 133,143 $ 114,092 $ 376,381 $ 414,274
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) September 30, 2020 December 31, 2019 Accounts receivable, net $ 100,223 $ 90,531 Contract assets (1) $ 1,015 $ 2,812 Unearned revenue $ 13,379 $ 11,963 Non-current unearned revenue $ 6,694 $ 6,012 (1) Included in other receivables on the Condensed Consolidated Balance Sheets.

Income Taxes (Tables)

Income Taxes (Tables)	9 Months Ended
	Sep. 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 September 30, 2020 and December 31, 2019 is as follows: September 30, 2020 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 49,212 $ (49,212 ) $ — International 9,892 (2,027 ) 7,865 Total $ 59,104 $ (51,239 ) $ 7,865 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)	9 Months Ended
	Sep. 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 nine months ended September 30, 2020 and 2019: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Service cost $ 325 $ 366 $ 942 $ 1,109 Interest cost 113 158 329 479 Expected return on plan assets (429 ) (346 ) (1,246 ) (1,049 ) Amortization of actuarial losses 248 198 720 600 Net periodic pension cost $ 257 $ 376 $ 745 $ 1,139

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 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 nine months ended September 30, 2020 and 2019: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Stock-based compensation expense included in cost of sales $ 101 $ 83 $ 303 $ 272 Selling, general and administrative expense 953 1,142 2,999 2,867 Research and development expense 556 646 1,754 2,045 Stock-based compensation expense included in operating expenses 1,509 1,788 4,753 4,912 Total stock-based compensation expense 1,610 1,871 5,056 5,184 Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock (384 ) (446 ) (1,205 ) (1,235 ) Total stock-based compensation expense, net of tax $ 1,226 $ 1,425 $ 3,851 $ 3,949
Summary of PSUs, RSUs and Restricted Stock Outstanding	The following table summarizes PSUs, RSUs and restricted stock outstanding as of December 31, 2019 and September 30, 2020 and the changes that occurred during the nine months ended September 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 (15 ) $ 12.76 PSUs, RSUs and restricted stock forfeited (586 ) $ 18.24 Unvested PSUs, RSUs and restricted stock outstanding, September 30, 2020 1,689 $ 11.83
Summary of Stock Options Outstanding	The following table summarizes stock options outstanding as of December 31, 2019 and September 30, 2020 and the changes that occurred during the nine months ended September 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 (352 ) $ 21.48 Stock options outstanding, September 30, 2020 3,220 $ 22.94 2.7 $ — Stock options exercisable, September 30, 2020 3,217 $ 22.95 2.7 $ —

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 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 September 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 $ 12,861 $ 149 $ — $ 13,010 Municipal fixed-rate bonds 3,093 32 (1 ) 3,124 Asset-backed bonds 8,472 115 — 8,587 Mortgage/Agency-backed bonds 10,964 127 (11 ) 11,080 U.S. government bonds 7,096 174 — 7,270 Foreign government bonds 1,032 3 — 1,035 Commercial paper 324 1 — 325 Variable-rate demand notes — — — — Other 442 — — 442 Available-for-sale debt securities held at fair value $ 44,284 $ 601 $ (12 ) $ 44,873 As 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 September 30, 2020, contractual maturities related to debt securities and other investments were as follows:
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 Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Gross realized gains on debt securities $ 70 $ 36 $ 303 $ 85 Gross realized losses on debt securities (6 ) (7 ) (45 ) (40 ) Total gain recognized, net $ 64 $ 29 $ 258 $ 45
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 nine months ended September 30, 2020 and 2019 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Realized gains (losses) on equity securities sold $ 623 $ (20 ) $ (1,485 ) $ (83 ) Unrealized gains (losses) on equity securities held 2,157 (225 ) 3,046 8,233 Total gain (loss) recognized, net $ 2,780 $ (245 ) $ 1,561 $ 8,150
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 September 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 $ 636 $ 636 $ — $ — U.S. government securities 300 300 — — Available-for-sale debt securities Corporate bonds 13,010 — 13,010 — Municipal fixed-rate bonds 3,124 — 3,124 — Asset-backed bonds 8,587 — 8,587 — Mortgage/Agency-backed bonds 11,080 — 11,080 — U.S. government bonds 7,270 7,270 — — Foreign government securities 1,035 — 1,035 — Commercial paper 325 — 325 — Variable-rate demand notes — — — Other 442 — — 442 Marketable equity securities Marketable equity securities – various industries 13,590 13,590 — — Deferred compensation plan assets 21,595 21,595 — — Other investments 1,276 1,276 — — Total $ 82,270 $ 44,667 $ 37,161 $ 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)	9 Months Ended
	Sep. 30, 2020
Inventory Disclosure [Abstract]
Components of Inventory	As of September 30, 2020 and December 31, 2019, inventory consisted of the following: September 30, December 31, (In thousands) 2020 2019 Raw materials $ 43,418 $ 36,987 Work in process 1,787 1,085 Finished goods 75,055 60,233 Total inventory $ 120,260 $ 98,305

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	9 Months Ended
	Sep. 30, 2020
Property Plant And Equipment [Abstract]
Property, Plant and Equipment	At September 30, 2020 and December 31, 2019, property, plant and equipment consisted of the following: September 30, December 31, (In thousands) 2020 2019 Land $ 4,575 $ 4,575 Building and land improvements 35,105 34,797 Building 68,160 68,157 Furniture and fixtures 19,981 19,959 Computer hardware and software 70,766 68,777 Engineering and other equipment 132,672 130,430 Total property, plant and equipment 331,259 326,695 Less: accumulated depreciation (266,906 ) (258,609 ) Total property, plant and equipment, net $ 64,353 $ 68,086

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2020
Intangible Assets Net Excluding Goodwill [Abstract]
Summary of Intangible Assets	Intangible assets as of September 30, 2020 and December 31, 2019 consisted of the following: September 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 $ 20,931 $ (7,369 ) $ 13,562 $ 22,356 $ (7,233 ) $ 15,123 Developed technology 8,200 (2,262 ) 5,938 10,170 (3,379 ) 6,791 Licensed technology 5,900 (1,666 ) 4,234 5,900 (1,174 ) 4,726 Supplier relationships 2,800 (2,800 ) — 2,800 (2,508 ) 292 Licensing agreements 560 (134 ) 426 560 (79 ) 481 Patents 500 (277 ) 223 500 (226 ) 274 Trade names 210 (128 ) 82 310 (176 ) 134 Total $ 39,101 $ (14,636 ) $ 24,465 $ 42,596 $ (14,775 ) $ 27,821
Estimated Future Amortization Expense Related to Intangible Assets	As of September 30, 2020, estimated future amortization expense of intangible assets was as follows: (In thousands) 2020 $ 1,041 2021 4,107 2022 3,482 2023 3,330 2024 3,236 Thereafter 9,269 Total $ 24,465

Leases (Tables)

Leases (Tables)	9 Months Ended
	Sep. 30, 2020
Leases [Abstract]
Schedule of Operating Lease Assets and Operating Lease Liabilities	As of September 30, 2020 and December 31, 2019, the Company’s operating lease assets and operating lease liabilities were as follows: (In thousands) Classification September 30, 2020 December 31, 2019 Assets Operating lease asset Other assets $ 5,503 $ 8,452 Total lease asset $ 5,503 $ 8,452 Liabilities Current operating lease liability Accrued expenses $ 1,731 $ 2,676 Non-current operating lease liability Other non-current liabilities 3,788 5,818 Total lease liability $ 5,519 $ 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 nine months ended September 30, 2020 and 2019 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Cost of sales $ 21 $ 16 $ 68 $ 49 Selling, general and administrative expenses 265 352 863 1,050 Research and development expenses 368 847 1,044 1,731 Total operating lease expense $ 654 $ 1,215 $ 1,975 $ 2,830
Schedule of Maturity of Operating Lease Liabilities	As of September 30, 2020 and December 31, 2019, operating lease liabilities included on the Condensed Consolidated Balance Sheets by future maturity were as follows: (In thousands) September 30, 2020 December 31, 2019 2020 $ 518 $ 2,856 2021 1,744 2,412 2022 1,514 1,705 2023 1,180 1,160 2024 499 482 Thereafter 276 264 Total lease payments 5,731 8,879 Less: Interest (212 ) (385 ) Present value of lease liabilities $ 5,519 $ 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 September 30, 2020 and December 31, 2019 : As of September 30, 2020 As of December 31, 2019 Weighted average remaining lease term (in years) Operating leases with USD functional currency 2.6 2.6 Operating leases with Euro functional currency 3.8 4.4 Weighted average discount rate Operating leases with USD functional currency 4.50 % 4.02 % Operating leases with Euro functional currency 1.81 % 1.84 %
Schedule of Supplemental Cash Flow Information Related to Operating Leases	Supplemental cash flow information related to operating leases is as follows: Three Months Ended Nine Months Ended September 30, September 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 $ 582 $ 775 $ 2,059 $ 2,383 Right-of-use assets obtained in exchange for lease obligations $ 138 $ 11,022 $ 231 $ 21,418
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 September 30, 2020 and December 31, 2019: (In thousands) September 30, 2020 December 31, 2019 Current minimum lease payments receivable (1) $ 811 $ 1,201 Non-current minimum lease payments receivable (2) 450 889 Total minimum lease payments receivable 1,261 2,090 Less: Current unearned revenue 235 365 Less: Non-current unearned revenue 70 163 Net investment in sales-type leases $ 956 $ 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 nine months ended September 30, 2020 and 2019 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Sales - Network Solutions $ 22 $ 47 $ 72 $ 1,668 Less: Cost of sales - Network Solutions 9 25 29 660 Gross profit $ 13 $ 22 $ 43 $ 1,008 Interest and dividend income $ 10 $ 92 $ 34 $ 278

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	9 Months Ended
	Sep. 30, 2020
Equity [Abstract]
Changes in Accumulated Other Comprehensive Income (Loss), Net of Tax by Component	The following tables present the changes in accumulated other comprehensive income (loss), net of tax, by component for the three months ended September 30, 2020 and 2019: Three Months Ended September 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 June 30, 2020 $ 206 $ (8,894 ) $ (7,043 ) $ 385 $ (15,346 ) Other comprehensive income before reclassifications 494 — 2,469 — 2,963 Amounts reclassified from accumulated other comprehensive income (loss) (539 ) 244 — — (295 ) Net current period other comprehensive income (45 ) 244 2,469 — 2,668 As of September 30, 2020 $ 161 $ (8,650 ) $ (4,574 ) $ 385 $ (12,678 ) Three Months Ended September 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 June 30, 2019 $ (271 ) $ (7,770 ) $ (6,439 ) $ 385 $ (14,095 ) Other comprehensive income before reclassifications (39 ) — (2,486 ) — (2,525 ) Amounts reclassified from accumulated other comprehensive income (loss) 24 90 — — 114 Net current period other comprehensive income (15 ) 90 (2,486 ) — (2,411 ) As of September 30, 2019 $ (286 ) $ (7,680 ) $ (8,925 ) $ 385 $ (16,506 ) (1) The following tables present the changes in accumulated other comprehensive income ( loss ) , net of tax , by component for the nine months ended September 30, 2020 and 2019 : Nine Months Ended September 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 444 — 2,718 — 3,162 Amounts reclassified from accumulated other comprehensive income 1 576 — — 577 Net current period other comprehensive income 445 576 2,718 — 3,739 As of September 30, 2020 $ 161 $ (8,650 ) $ (4,574 ) $ 385 $ (12,678 ) Nine Months Ended September 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 372 — (3,113 ) — (2,741 ) Amounts reclassified from accumulated other comprehensive income (loss) (95 ) 361 — — 266 Amounts reclassified to retained earnings (1) — — — 385 385 Net current period other comprehensive income (loss) 277 361 (3,113 ) 385 (2,090 ) As of September 30, 2019 $ (286 ) $ (7,680 ) $ (8,925 ) $ 385 $ (16,506 ) (1)
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	The following tables present the details of reclassifications out of accumulated other comprehensive income (loss) for the three months ended September 30, 2020 and 2019: Three Months Ended September 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 $ 728 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (354 ) (1) Total reclassifications for the period, before tax 374 Tax expense (79 ) Total reclassifications for the period, net of tax $ 295 (1) Three Months Ended September 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 losses on sales of securities $ (32 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (130 ) (1) Total reclassifications for the period, before tax (162 ) Tax benefit 48 Total reclassifications for the period, net of tax $ (114 ) (1) The following tables present the details of reclassifications out of accumulated other comprehensive loss for the nine months ended September 30, 2020 and 2019: Nine Months Ended September 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 $ (1 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (835 ) (1) Total reclassifications for the period, before tax (836 ) Tax benefit 259 Total reclassifications for the period, net of tax $ (577 ) (1) Nine Months Ended September 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 on available-for-sale securities: Net realized gains on sales of securities $ 128 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses (523 ) (1) Total reclassifications for the period, before tax (395 ) Tax benefit 129 Total reclassifications for the period, net of tax $ (266 ) (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 loss for the three months ended September 30, 2020 and 2019: Three Months Ended Three Months Ended September 30, 2020 September 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 $ 668 $ (174 ) $ 494 $ (53 ) $ 14 $ (39 ) Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss) (728 ) 189 (539 ) 32 (8 ) 24 Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss) 354 (110 ) 244 130 (40 ) 90 Foreign currency translation adjustment 2,469 — 2,469 (2,486 ) — (2,486 ) Total Other Comprehensive Income (Loss) $ 2,763 $ (95 ) $ 2,668 $ (2,377 ) $ (34 ) $ (2,411 ) The following table presents the tax effects related to the change in each component of other comprehensive income (loss) for the nine months ended September 30, 2020 and 2019: Nine Months Ended Nine Months Ended September 30, 2020 September 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 $ 600 $ (156 ) $ 444 $ 503 $ (131 ) $ 372 Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss) 1 — 1 (128 ) 33 (95 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss) 835 (259 ) 576 523 (162 ) 361 Foreign currency translation adjustment 2,718 — 2,718 (3,113 ) — (3,113 ) Total Other Comprehensive Income (Loss) $ 4,154 $ (415 ) $ 3,739 $ (2,215 ) $ (260 ) $ (2,475 )

Earnings (Loss) Per Share (Tabl

Earnings (Loss) Per Share (Tables)	9 Months Ended
	Sep. 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 nine months ended September 30, 2020 and 2019 is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share amounts) 2020 2019 2020 2019 Numerator Net income (loss) $ 5,481 $ (46,123 ) $ (3,736 ) $ (41,358 ) Denominator Weighted average number of shares – basic 47,957 47,824 47,957 47,803 Effect of dilutive securities PSUs, RSUs and restricted stock 467 — — — Weighted average number of shares – diluted 48,424 47,824 47,957 47,803 Earnings (loss) per share – basic $ 0.11 $ (0.96 ) $ (0.08 ) $ (0.87 ) Earnings (loss) per share – diluted $ 0.11 $ (0.96 ) $ (0.08 ) $ (0.87 )

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 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 nine months ended September 30, 2020 and 2019. Three Months Ended September 30, 2020 September 30, 2019 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 115,229 $ 52,434 $ 94,018 $ 37,574 Services & Support 17,914 6,528 20,074 8,757 Total $ 133,143 $ 58,962 $ 114,092 $ 46,331 Nine Months Ended September 30, 2020 September 30, 2019 (In thousands) Sales Gross Profit Sales Gross Profit Network Solutions $ 323,924 $ 145,432 $ 359,007 $ 151,654 Services & Support 52,457 18,602 55,267 20,304 Total $ 376,381 $ 164,034 $ 414,274 $ 171,958
Disaggregate of Revenue by Reportable Segment and Revenue Category	The following tables disaggregate revenue by reportable segment and revenue category for the three and nine months ended September 30, 2020 and 2019: Three Months Ended September 30, 2020 September 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 71,919 $ 13,504 $ 85,423 $ 48,902 $ 16,212 $ 65,114 Subscriber Solutions & Experience 40,843 2,282 43,125 40,382 2,094 42,476 Traditional & Other Products 2,467 2,128 4,595 4,734 1,768 6,502 Total $ 115,229 $ 17,914 $ 133,143 $ 94,018 $ 20,074 $ 114,092 Nine Months Ended September 30, 2020 September 30, 2019 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 194,695 $ 39,470 $ 234,165 $ 230,837 $ 43,476 $ 274,313 Subscriber Solutions & Experience 118,907 6,790 125,697 113,545 6,186 119,731 Traditional & Other Products 10,322 6,197 16,519 14,625 5,605 20,230 Total $ 323,924 $ 52,457 $ 376,381 $ 359,007 $ 55,267 $ 414,274 The table below presents sales information by category for the three and nine months ended September 30, 2020 and 2019: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Access & Aggregation $ 85,423 $ 65,114 $ 234,165 $ 274,313 Subscriber Solutions & Experience 43,125 42,476 125,697 119,731 Traditional & Other Products 4,595 6,502 16,519 20,230 Total $ 133,143 $ 114,092 $ 376,381 $ 414,274
Sales Information by Geographic Area	The following table presents sales information by geographic area for the three and nine months ended September 30, 2020 and 2019: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 United States $ 92,838 $ 83,144 $ 256,287 $ 230,960 International 40,305 30,948 120,094 183,314 Total $ 133,143 $ 114,092 $ 376,381 $ 414,274

Liability for Warranty Returns

Liability for Warranty Returns (Tables)	9 Months Ended
	Sep. 30, 2020
Product Warranties Disclosures [Abstract]
Summary of Reconciliation of Warranty Expense and Related Write-off Activity	A reconciliation of warranty expense and related write-off activity for the three and nine months ended September 30, 2020 and 2019 is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Balance at beginning of period $ 7,294 $ 8,972 $ 8,394 $ 8,623 Plus: Amounts charged to cost and expenses 632 816 970 3,796 Less: Deductions (734 ) (1,131 ) (2,172 ) (3,762 ) Balance at end of period $ 7,192 $ 8,657 $ 7,192 $ 8,657

Current Expected Credit Losses

Current Expected Credit Losses (Tables)	9 Months Ended
	Sep. 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 $ 58 $ 227 $ 426 $ 153 $ 89 $ 3 $ 956 Non-performing — — — — — — — Total $ 58 $ 227 $ 426 $ 153 $ 89 $ 3 $ 956
Available-for-Sale Debt Securities in Unrealized Loss Position	The Company had 45 positions in available-for-sale debt securities that were in an unrealized loss position as of September 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 — — — — — — Municipal fixed-rate bonds 394 (1 ) — — 394 (1 ) Asset-backed bonds 396 — — — 396 — Mortgage/Agency-backed bonds 3,199 (11 ) — — 3,199 (11 ) U.S. government bonds 800 — — — 800 — Foreign government bonds 75 — — — 75 — Total $ 4,864 $ (12 ) $ — $ — $ 4,864 $ (12 ) 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 ) Foreign government bonds 371 (1 ) — — 371 (1 ) Total $ 8,965 $ (19 ) $ 136 $ (2 ) $ 9,101 $ (21 )

Restructuring (Tables)

Restructuring (Tables)	9 Months Ended
	Sep. 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 on the Condensed Consolidated Balance Sheets as of September 30, 2020 and December 31, 2019, is as follows: Three Months Ended Nine Months Ended (In thousands) September 30, 2020 September 30, 2020 Balance at beginning of period $ 358 $ 1,568 Plus: Amounts charged to expense 1,903 3,648 Less: Amounts paid (542 ) (3,497 ) Balance as of September 30, 2020 $ 1,719 $ 1,719 (In thousands) December 31, 2019 Balance as of December 31, 2018 $ 185 Plus: Amounts charged to 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 Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Cost of sales 232 62 288 747 Selling, general and administrative expenses $ 1,050 $ 531 $ 1,622 $ 2,078 Research and development expenses 621 602 1,738 1,833 Total restructuring expenses $ 1,903 $ 1,195 $ 3,648 $ 4,658 The following table represents the components of restructuring expenses by geographic area: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2020 2019 2020 2019 Domestic $ 448 $ 1,116 $ 2,191 $ 1,941 International 1,455 79 1,457 2,717 Total restructuring expenses $ 1,903 $ 1,195 $ 3,648 $ 4,658

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended					6 Months Ended	9 Months Ended
	Sep. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020	Dec. 31, 2019
Summary Of Significant Accounting Policy [Line Items]
Life insurance proceeds received								$ 1,000
Effect on adoption of ASU	$ 64,353						$ 64,353			$ 68,086
Effect on adoption of ASU	20,409						20,409			19,883
Tax benefit in other comprehensive income (loss)	$ 95		$ 34				$ 415	$ 260
ASU 2016-13 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true						true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020						Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true						true
ASU 2017-04 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true						true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020						Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true						true
ASU 2018-13 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true						true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020						Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true						true
ASU 2018-15 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true						true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Jan. 1, 2020						Jan. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true						true
Effect on adoption of ASU										68,086
Effect on adoption of ASU										$ 19,883
ASU 2018-15 [Member] | Revision of Prior Period, Accounting Standards Update, Adjustment [Member]
Summary Of Significant Accounting Policy [Line Items]
Effect on adoption of ASU									$ (5,600)
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)
ASU 2019-12 [Member]
Summary Of Significant Accounting Policy [Line Items]
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]	true						true
Change in Accounting Principle, Accounting Standards Update, Adoption Date	Apr. 1, 2020						Apr. 1, 2020
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]	true						true
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	Sep. 30, 2020	Dec. 31, 2019
Summary Of Significant Accounting Policy [Line Items]
Property, plant and equipment, net	$ 64,353	$ 68,086
Other assets	$ 20,409	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 Loss and Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Summary Of Significant Accounting Policy [Line Items]
Net loss	$ 5,481	$ 752	$ (9,969)	$ (46,123)	$ 3,995	$ 770	$ (3,736)	$ (41,358)
Net cash provided by operating activities							$ (5,317)	10,082
ASU 2018-15 [Member]
Summary Of Significant Accounting Policy [Line Items]
Net loss				(46,123)				(41,358)
Net cash provided by operating activities								10,082
Pre-Adoption [Member]
Summary Of Significant Accounting Policy [Line Items]
Net loss				$ (46,123)				(41,358)
Net cash provided by operating activities								$ 10,082

Summary of Significant Accoun_7

Summary of Significant Accounting Policies - Schedule of Capitalized Implementation Costs Incurred with Hosting Arrangements, Included in Other Assets on Condensed Consolidated Balance Sheet (Detail) $ in Thousands	Sep. 30, 2020USD ($)
Hosting Arrangement Service Contract [Abstract]
Implementation costs - hosting arrangements	$ 10,455
Implementation costs - hosting arrangements, net	$ 10,455

Cash, Cash Equivalents and Re_3

Cash, Cash Equivalents and Restricted Cash - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Abstract]
Cash and cash equivalents	$ 71,081,000	$ 73,773,000
Restricted cash	322,000	$ 0
Cash, cash equivalents and restricted cash	$ 71,403,000

Cash, Cash Equivalents and Re_4

Cash, Cash Equivalents and Restricted Cash - Additional Information (Detail) - USD ($)	Sep. 30, 2020	Dec. 31, 2019
Cash And Cash Equivalents [Abstract]
Restricted cash	$ 322,000	$ 0

Revenue - Additional Informatio

Revenue - Additional Information (Detail)	3 Months Ended		9 Months Ended
	Sep. 30, 2020USD ($)	Sep. 30, 2019USD ($)	Sep. 30, 2020USD ($)Category	Sep. 30, 2019USD ($)	Dec. 31, 2019USD ($)
Revenue [Line Items]
Number of categories | Category			3
Remaining performance obligations	$ 0		$ 0
Recognized revenue	1,500,000	$ 1,200,000	9,600,000	$ 11,700,000
Other Than Maintenance Services [Member]
Revenue [Line Items]
Remaining performance obligations	$ 16,500,000		$ 16,500,000		$ 13,600,000

Revenue - Disaggregate of Reven

Revenue - Disaggregate of Revenue by Reportable Segment and Revenue Category (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Revenue	$ 133,143	$ 114,092	$ 376,381	$ 414,274
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	85,423	65,114	234,165	274,313
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	43,125	42,476	125,697	119,731
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	4,595	6,502	16,519	20,230
Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	115,229	94,018	323,924	359,007
Network Solutions [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	71,919	48,902	194,695	230,837
Network Solutions [Member] | Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	40,843	40,382	118,907	113,545
Network Solutions [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	2,467	4,734	10,322	14,625
Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue	17,914	20,074	52,457	55,267
Services & Support [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	13,504	16,212	39,470	43,476
Services & Support [Member] | Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	2,282	2,094	6,790	6,186
Services & Support [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 2,128	$ 1,768	$ 6,197	$ 5,605

Revenue - Additional Informat_2

Revenue - Additional Information (Detail1) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2020-10-01	Sep. 30, 2020
Revenue [Line Items]
Remaining performance obligations, percentage	59.00%
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	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Revenue From Contract With Customer [Abstract]
Accounts receivable, net	$ 100,223	$ 90,500	$ 90,531
Contract assets	1,015	$ 2,800	2,812
Unearned revenue	13,379		11,963
Non-current unearned revenue	$ 6,694		$ 6,012

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Income Tax Disclosure [Line Items]
Effective tax rate expense (benefit)	9.30%	150.60%	(36.80%)	197.10%
Income tax benefit, result of CARES act of 2020			$ 7,800
Effective tax rate reduction related to transfer pricing study		7.10%		7.10%
Additional change in valuation allowances related to domestic operations	$ 1,000
Additional income tax benefit result of CARES act of 2020	400
Deferred tax assets, gross	59,104		59,104		$ 56,177
Valuation allowance established against deferred tax assets	51,239		51,239		48,616
Deferred tax assets	7,865		7,865		7,561
Domestic [Member]
Income Tax Disclosure [Line Items]
Valuation allowance established against deferred tax assets		$ 37,100	2,600	$ 37,100
Deferred tax assets, gross	49,212		49,212		46,266
Valuation allowance established against deferred tax assets	$ 49,212		$ 49,212		$ 46,266

Income Taxes - Summary of Suppl

Income Taxes - Summary of Supplemental Balance Sheet Information Related to Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	$ 59,104	$ 56,177
Valuation Allowance	(51,239)	(48,616)
Deferred Tax Assets, net	7,865	7,561
Domestic [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	49,212	46,266
Valuation Allowance	(49,212)	(46,266)
International [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	9,892	9,911
Valuation Allowance	(2,027)	(2,350)
Deferred Tax Assets, net	$ 7,865	$ 7,561

Pension Benefit Plan - Summariz

Pension Benefit Plan - Summarization of Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Compensation And Retirement Disclosure [Abstract]
Service cost	$ 325	$ 366	$ 942	$ 1,109
Interest cost	113	158	329	479
Expected return on plan assets	(429)	(346)	(1,246)	(1,049)
Amortization of actuarial losses	248	198	720	600
Net periodic pension cost	$ 257	$ 376	$ 745	$ 1,139

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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,610	$ 1,871	$ 5,056	$ 5,184
Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock	(384)	(446)	(1,205)	(1,235)
Total stock-based compensation expense, net of tax	1,226	1,425	3,851	3,949
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	101	83	303	272
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	953	1,142	2,999	2,867
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	556	646	1,754	2,045
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	$ 1,509	$ 1,788	$ 4,753	$ 4,912

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of PSUs, RSUs and Restricted Stock Outstanding (Detail) shares in Thousands	9 Months Ended
	Sep. 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	(15)
Number of Shares, PSUs, RSUs and restricted stock forfeited | shares	(586)
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, ending balance | shares	1,689
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	12.76
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	18.24
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	$ 11.83

Stock-Based Compensation (PSUs,

Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)shares
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Options available for issuance under stockholders-approved equity plan	3,600,000
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
Forfeiture of stock increase in issuance of common stock	1
Contractual term	10 years
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 | $	$ 10.6
Recognition period of unvested compensation expense	2 years 3 months 18 days
Performance-Based PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to other than options | $	$ 2.3
Recognition period of unvested compensation expense	2 years 3 months 18 days
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
Stock Options [Member] | 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	9 Months Ended	12 Months Ended
	Sep. 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	(352)
Number of Stock Options, Stock options outstanding, Ending Balance	3,220	3,572
Number of Stock Options, Stock options exercisable	3,217
Weighted Avg. Exercise Price, Stock options outstanding, Beginning Balance	$ 22.88
Weighted Avg. Exercise Price, Stock options expired	21.48
Weighted Avg. Exercise Price, Stock options outstanding, Ending Balance	22.94	$ 22.88
Weighted Avg. Exercise Price, Stock options exercisable	$ 22.95
Weighted Avg. Remaining Contractual Life In Years, Stock options outstanding	2 years 8 months 12 days	3 years 4 months 24 days
Weighted Avg. Remaining Contractual Life in Years, Stock options exercisable	2 years 8 months 12 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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 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 unvested stock options	$ 1		$ 1
Recognition period of unvested compensation expense			1 month 6 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	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 44,284		$ 37,528
Gross Unrealized Gains	601		153
Gross Unrealized Losses	(12)		(21)
Fair Value	44,873	$ 37,700	37,660
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	12,861		9,304
Gross Unrealized Gains	149		80
Fair Value	13,010		9,384
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	3,093		930
Gross Unrealized Gains	32
Gross Unrealized Losses	(1)
Fair Value	3,124		930
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	8,472		6,867
Gross Unrealized Gains	115		26
Gross Unrealized Losses			(3)
Fair Value	8,587		6,890
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	10,964		6,944
Gross Unrealized Gains	127		26
Gross Unrealized Losses	(11)		(8)
Fair Value	11,080		6,962
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	7,096		12,311
Gross Unrealized Gains	174		21
Gross Unrealized Losses			(9)
Fair Value	7,270		12,323
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,032		372
Gross Unrealized Gains	3
Gross Unrealized Losses			(1)
Fair Value	1,035		371
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	324
Gross Unrealized Gains	1
Fair Value	325
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost			800
Fair Value			$ 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	Sep. 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	$ 44,873	$ 37,700	$ 37,660
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	2,900
One to two years	3,752
Two to three years	6,122
Three to five years	236
Available-for-sale debt securities, Fair Value/Carrying Value	13,010		9,384
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	737
One to two years	1,183
Two to three years	908
Three to five years	296
Available-for-sale debt securities, Fair Value/Carrying Value	3,124		930
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	696
One to two years	956
Two to three years	615
Three to five years	4,817
Five to ten years	946
More than ten years	557
Available-for-sale debt securities, Fair Value/Carrying Value	8,587		6,890
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	208
One to two years	1,256
Two to three years	2,775
Three to five years	1,079
Five to ten years	1,507
More than ten years	4,255
Available-for-sale debt securities, Fair Value/Carrying Value	11,080		6,962
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	500
One to two years	826
Two to three years	5,492
Three to five years	452
Available-for-sale debt securities, Fair Value/Carrying Value	7,270		12,323
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	75
One to two years	463
Two to three years	497
Available-for-sale debt securities, Fair Value/Carrying Value	1,035		$ 371
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	325
Available-for-sale debt securities, Fair Value/Carrying Value	325
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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investments Debt And Equity Securities [Abstract]
Gross realized gains on debt securities	$ 70	$ 36	$ 303	$ 85
Gross realized losses on debt securities	(6)	(7)	(45)	(40)
Total gain recognized, net	$ 64	$ 29	$ 258	$ 45

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019	Jan. 01, 2020	Dec. 31, 2019
Schedule of Investments [Line Items]
Purchase an available-for-sale debt securities with credit deterioration	$ 0			$ 0
Transfer from investments			$ 3,400,000
Carrying value							$ 3,400,000
Note receivable, noncurrent	900,000			900,000		$ 900,000
Asset impairments		$ 3,872,000		65,000	$ 3,872,000
Carrying value of investment	1,800,000			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			4,300,000
Asset impairments				0
Long-term Investments [Member]
Schedule of Investments [Line Items]
Note receivable, noncurrent	$ 900,000			$ 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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Investments Debt And Equity Securities [Abstract]
Realized gains (losses) on equity securities sold	$ 623	$ (20)	$ (1,485)	$ (83)
Unrealized gains (losses) on equity securities held	2,157	(225)	3,046	8,233
Total gain (loss) recognized, net	$ 2,780	$ (245)	$ 1,561	$ 8,150

Investments - Cash Equivalents

Investments - Cash Equivalents and Investments held at Fair Value (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	$ 44,873	$ 37,700	$ 37,660
Marketable equity securities	1,800
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Other investments	1,276		2,442
Total	82,270		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	1,276		2,442
Total	44,667		73,571
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	37,161		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	636		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	636		1,309
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	7,270		12,323
U.S. Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	300
Available-for-sale debt securities	7,270		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	300
Available-for-sale debt securities	7,270		12,323
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	13,010		9,384
Corporate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	13,010		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	13,010		9,384
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	3,124		930
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	3,124		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	3,124		930
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	8,587		6,890
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	8,587		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	8,587		6,890
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	11,080		6,962
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	11,080		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	11,080		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	13,590		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	13,590		35,501
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	1,035		371
Foreign Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	1,035		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	1,035		371
Commercial Paper [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	325
Commercial Paper [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	325
Commercial Paper [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	325
Variable Rate Demand Notes [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities			800
Variable Rate Demand Notes [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities			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			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	21,595		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	$ 21,595		$ 21,698

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Raw materials	$ 43,418	$ 36,987
Work in process	1,787	1,085
Finished goods	75,055	60,233
Total inventory	$ 120,260	$ 98,305

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Sep. 30, 2020	Dec. 31, 2019
Inventory Disclosure [Abstract]
Inventory valuation reserves	$ 38	$ 34.1

Property, Plant and Equipment -

Property, Plant and Equipment - Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Property Plant And Equipment [Abstract]
Land	$ 4,575	$ 4,575
Building and land improvements	35,105	34,797
Building	68,160	68,157
Furniture and fixtures	19,981	19,959
Computer hardware and software	70,766	68,777
Engineering and other equipment	132,672	130,430
Total property, plant and equipment	331,259	326,695
Less: accumulated depreciation	(266,906)	(258,609)
Total property, plant and equipment, net	$ 64,353	$ 68,086

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Property Plant And Equipment [Abstract]
Impairment losses of long-lived assets			$ 0
Depreciation	$ 3,100,000	$ 3,100,000	$ 9,100,000	$ 9,300,000

Goodwill - Additional Informati

Goodwill - Additional Information (Detail) - USD ($)	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2020	Sep. 30, 2020	Dec. 31, 2019
Goodwill [Line Items]
Goodwill		$ 7,000,000	$ 7,000,000
Impairment of goodwill	$ 0	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	Sep. 30, 2020	Dec. 31, 2019
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 39,101	$ 42,596
Accumulated Amortization	(14,636)	(14,775)
Net Book Value	24,465	27,821
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	20,931	22,356
Accumulated Amortization	(7,369)	(7,233)
Net Book Value	13,562	15,123
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	8,200	10,170
Accumulated Amortization	(2,262)	(3,379)
Net Book Value	5,938	6,791
Licensed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,900	5,900
Accumulated Amortization	(1,666)	(1,174)
Net Book Value	4,234	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	(134)	(79)
Net Book Value	426	481
Patent [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	500	500
Accumulated Amortization	(277)	(226)
Net Book Value	223	274
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	210	310
Accumulated Amortization	(128)	(176)
Net Book Value	$ 82	$ 134

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Intangible Assets Net Excluding Goodwill [Abstract]
Impairment losses of intangible assets		$ 0		$ 0
Amortization expense	$ 1,000,000		$ 1,300,000	$ 3,400,000	$ 4,000,000

Intangible Assets - Estimated F

Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Finite Lived Intangible Assets Future Amortization Expense [Abstract]
2020	$ 1,041
2021	4,107
2022	3,482
2023	3,330
2024	3,236
Thereafter	9,269
Net Book Value	$ 24,465	$ 27,821

Leases - Additional Information

Leases - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 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	$ 6	$ 100	$ 20	$ 300
Variable lease cost	100	$ 300	400	$ 700
Operating lease payments, option to extend	$ 300		$ 300
Minimum [Member]
Lessor and Lessee Lease Description [Line Items]
Operating lease, remaining lease terms	1 month		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		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	Sep. 30, 2020	Dec. 31, 2019
ASSETS
Operating lease asset	$ 5,503	$ 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	$ 1,731	$ 2,676
Operating lease, liability, current, statement of financial position [extensible list]	us-gaap:AccruedLiabilitiesCurrent	us-gaap:AccruedLiabilitiesCurrent
Non-current operating lease liability	$ 3,788	$ 5,818
Operating lease, liability, noncurrent, statement of financial position [extensible list]	us-gaap:OtherLiabilitiesNoncurrent	us-gaap:OtherLiabilitiesNoncurrent
Total lease liability	$ 5,519	$ 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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Lessor Lease Description [Line Items]
Total operating lease expense	$ 654	$ 1,215	$ 1,975	$ 2,830
Selling, General and Administrative Expenses [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	265	352	863	1,050
Research and Development Expenses [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	368	847	1,044	1,731
Cost of Sales [Member]
Lessor Lease Description [Line Items]
Total operating lease expense	$ 21	$ 16	$ 68	$ 49

Leases - Schedule of Maturity o

Leases - Schedule of Maturity of Operating Lease Liabilities (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Dec. 31, 2019
Operating Lease Liabilities Payments Due [Abstract]
2020	$ 518
2020	1,744	$ 2,856
2022	1,514	2,412
2023	1,180	1,705
2024	499	1,160
2024		482
Thereafter	276
Thereafter		264
Total lease payments	5,731	8,879
Less: Interest	(212)	(385)
Present value of lease liabilities	$ 5,519	$ 8,494

Leases - Schedule of Weighted A

Leases - Schedule of Weighted Average Remaining Lease Terms and Weighted Average Discount Rates (Detail)	Sep. 30, 2020	Dec. 31, 2019
USD
Weighted average remaining lease term (in years)
Operating leases with functional currency	2 years 7 months 6 days	2 years 7 months 6 days
Weighted average discount rate
Operating leases with functional currency	4.50%	4.02%
Euro
Weighted average remaining lease term (in years)
Operating leases with functional currency	3 years 9 months 18 days	4 years 4 months 24 days
Weighted average discount rate
Operating leases with functional currency	1.81%	1.84%

Leases - Schedule of Supplement

Leases - Schedule of Supplemental Cash Flow Information Related to Operating Leases (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Cash paid for amounts included in the measurement of operating lease assets / liabilities
Cash used in operating activities related to operating leases	$ 582	$ 775	$ 2,059	$ 2,383
Right-of-use assets obtained in exchange for lease obligations	$ 138	$ 11,022	$ 231	$ 21,418

Leases - Net Investment in Sale

Leases - Net Investment in Sales-Type Leases (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Sales Type Leases Net Investment In Leases [Abstract]
Current minimum lease payments receivable	$ 811		$ 1,201
Non-current minimum lease payments receivable	450		889
Total minimum lease payments receivable	1,261		2,090
Less: Current unearned revenue	235		365
Less: Non-current unearned revenue	70		163
Net investment in sales-type leases	$ 956	$ 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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Sales [Member] | Network Solutions [Member]
Lessor Lease Description [Line Items]
Sales type leases	$ 22	$ 47	$ 72	$ 1,668
Cost of Sales [Member] | Network Solutions [Member]
Lessor Lease Description [Line Items]
Sales type leases	9	25	29	660
Gross Profit [Member]
Lessor Lease Description [Line Items]
Sales type leases	13	22	43	1,008
Interest and Dividend Income [Member]
Lessor Lease Description [Line Items]
Sales type leases	$ 10	$ 92	$ 34	$ 278

Alabama State Industrial Deve_2

Alabama State Industrial Development Authority Financing and Economic Incentives - Additional Information (Detail) - USD ($) $ in Thousands	Jan. 02, 2020	Sep. 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)	9 Months Ended
	Sep. 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 Income (Loss), Net of Tax by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 364,194	$ 445,975	$ 380,426	$ 446,279
Other comprehensive income (loss) before reclassifications	2,963	(2,525)	3,162	(2,741)
Amounts reclassified from accumulated other comprehensive income (loss)	(295)	114	577	266
Amounts reclassified to retained earnings				385
Net current period other comprehensive income (loss)	2,668	(2,411)	3,739	(2,090)
Ending Balance	369,593	394,955	369,593	394,955
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	206	(271)	(284)	(563)
Other comprehensive income (loss) before reclassifications	494	(39)	444	372
Amounts reclassified from accumulated other comprehensive income (loss)	(539)	24	1	(95)
Net current period other comprehensive income (loss)	(45)	(15)	445	277
Ending Balance	161	(286)	161	(286)
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(8,894)	(7,770)	(9,226)	(8,041)
Amounts reclassified from accumulated other comprehensive income (loss)	244	90	576	361
Net current period other comprehensive income (loss)	244	90	576	361
Ending Balance	(8,650)	(7,680)	(8,650)	(7,680)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(7,043)	(6,439)	(7,292)	(5,812)
Other comprehensive income (loss) before reclassifications	2,469	(2,486)	2,718	(3,113)
Net current period other comprehensive income (loss)	2,469	(2,486)	2,718	(3,113)
Ending Balance	(4,574)	(8,925)	(4,574)	(8,925)
Accumulated Other Comprehensive Income [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(15,346)	(14,095)	(16,417)	(14,416)
Ending Balance	$ (12,678)	$ (16,506)	$ (12,678)	$ (16,506)

Stockholders' Equity - Reclassi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Income (Loss) Before Income Taxes	$ 6,043			$ (18,406)			$ (5,907)	$ (13,921)
Tax benefit (expense)	(562)			(27,717)			2,171	(27,437)
Net Income (Loss)	5,481	$ 752	$ (9,969)	(46,123)	$ 3,995	$ 770	(3,736)	(41,358)
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	(354)			(130)			(835)	(523)
Income (Loss) Before Income Taxes	374			(162)			(836)	(395)
Tax benefit (expense)	(79)			48			259	129
Net Income (Loss)	295			(114)			(577)	(266)
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)	$ 728			$ (32)			$ (1)	$ 128

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						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Equity [Abstract]
Unrealized gain (loss) on available-for-sale securities, Before-Tax Amount	$ 668			$ (53)			$ 600	$ 503
Unrealized gain (loss) on available-for-sale securities, Tax (Expense) Benefit	(174)			14			(156)	(131)
Unrealized gain (loss) on available-for-sale securities, Net-of-Tax Amount	494			(39)			444	372
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Before-Tax Amount	(728)			32			1	(128)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Tax (Expense) Benefit	189			(8)				33
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Net-of-Tax Amount	(539)			24			1	(95)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Before-Tax Amount	354			130			835	523
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Tax (Expense) Benefit	(110)			(40)			(259)	(162)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Net-of-Tax Amount	244			90			576	361
Foreign currency translation adjustment, Before-Tax Amount	2,469			(2,486)			2,718	(3,113)
Foreign currency translation adjustment, Net-of-Tax Amount	2,469			(2,486)			2,718	(3,113)
Total Other Comprehensive Income (Loss), Before-Tax Amount	2,763			(2,377)			4,154	(2,215)
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	(95)			(34)			(415)	(260)
Other Comprehensive Income (Loss), net of tax	$ 2,668	$ 2,463	$ (1,392)	$ (2,411)	$ 790	$ (854)	$ 3,739	$ (2,475)

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						9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2020	Sep. 30, 2019
Numerator
Net income (loss)	$ 5,481	$ 752	$ (9,969)	$ (46,123)	$ 3,995	$ 770	$ (3,736)	$ (41,358)
Denominator
Weighted average number of shares – basic	47,957			47,824			47,957	47,803
Effect of dilutive securities
PSUs, RSUs and restricted stock	467
Weighted average number of shares – diluted	48,424			47,824			47,957	47,803
Earnings (loss) per share – basic	$ 0.11			$ (0.96)			$ (0.08)	$ (0.87)
Earnings (loss) per share – diluted	$ 0.11			$ (0.96)			$ (0.08)	$ (0.87)

Earnings (Loss) Per Share - Add

Earnings (Loss) Per Share - Additional Information (Detail) - shares shares in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted earnings per share	3,400	3,900	4,300	2,800
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	18	100	100	100

Segment Information - Additiona

Segment Information - Additional Information (Detail)	9 Months Ended
	Sep. 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		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Segment Reporting Information [Line Items]
Sales	$ 133,143	$ 114,092	$ 376,381	$ 414,274
Gross Profit	58,962	46,331	164,034	171,958
Network Solutions [Member]
Segment Reporting Information [Line Items]
Sales	115,229	94,018	323,924	359,007
Gross Profit	52,434	37,574	145,432	151,654
Services & Support [Member]
Segment Reporting Information [Line Items]
Sales	17,914	20,074	52,457	55,267
Gross Profit	$ 6,528	$ 8,757	$ 18,602	$ 20,304

Segment Information - Sales Inf

Segment Information - Sales Information by Category (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Disaggregation Of Revenue [Line Items]
Revenue	$ 133,143	$ 114,092	$ 376,381	$ 414,274
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	85,423	65,114	234,165	274,313
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	43,125	42,476	125,697	119,731
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 4,595	$ 6,502	$ 16,519	$ 20,230

Segment Information- Sales Info

Segment Information- Sales Information by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Revenue from External Customer [Line Items]
Sales	$ 133,143	$ 114,092	$ 376,381	$ 414,274
United States [Member]
Revenue from External Customer [Line Items]
Sales	92,838	83,144	256,287	230,960
International [Member]
Revenue from External Customer [Line Items]
Sales	$ 40,305	$ 30,948	$ 120,094	$ 183,314

Liability for Warranty Return_2

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2020	Jun. 30, 2020	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 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	$ 7,192	$ 7,294	$ 8,394	$ 8,657	$ 8,972	$ 8,623

Liability for Warranty Return_3

Liability for Warranty Returns - Summary of Reconciliation of Warranty Expense and Related Write-off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 7,294	$ 8,972	$ 8,394	$ 8,623
Plus: Amounts charged to cost and expenses	632	816	970	3,796
Less: Deductions	(734)	(1,131)	(2,172)	(3,762)
Balance at end of period	$ 7,192	$ 8,657	$ 7,192	$ 8,657

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail)	Mar. 31, 2020Officer	Oct. 17, 2019Officer	Sep. 30, 2020USD ($)	Oct. 08, 2020USD ($)	Dec. 31, 2019USD ($)
Contingencies And Commitments [Line Items]
Commitments related to performance bonds			$ 12,000,000		$ 9,300,000
Commitments related to performance bonds expiration month and year			2024-08
Letter of credit secured by pledge of a portion of fixed income securities			$ 5,900,000
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 [Member]
Contingencies And Commitments [Line Items]
Letter of credit secured by pledge of a portion of fixed income securities			300,000
Long-term Investments [Member]
Contingencies And Commitments [Line Items]
Letter of credit secured by pledge of a portion of fixed income securities			5,600,000
Minimum [Member]
Contingencies And Commitments [Line Items]
Collateral value required to be maintained			4,500,000
Letter of credit secured by pledge of collateral value fluctuation between restricted cash and long term investment			13,000,000
Minimum [Member] | Subsequent Event [Member]
Contingencies And Commitments [Line Items]
Collateral value required to be maintained				$ 9,000,000
Maximum [Member]
Contingencies And Commitments [Line Items]
Letter of credit secured by pledge of collateral value fluctuation between restricted cash and long term investment			$ 15,000,000
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 ($)	Sep. 30, 2020USD ($)Position	Sep. 30, 2020USD ($)Position	Dec. 31, 2019USD ($)
Financing Receivable Allowance For Credit Losses [Line Items]
Outstanding accounts receivable	$ 90,500,000	$ 100,223,000	$ 100,223,000	$ 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	1,015,000	1,015,000	2,812,000
Allowance for credit losses related to contract assets	0	0	0
Outstanding net investment in sales-type leases	1,600,000	956,000	956,000	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	$ 44,873,000	$ 44,873,000	$ 37,660,000
Number of positions in available-for-sale debt securities, unrealized loss position | Position		45	45
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	Sep. 30, 2020	Jan. 01, 2020	Dec. 31, 2019
Sales Type Lease Net Investment In Lease Credit Quality Indicator [Line Items]
2020	$ 58
2019	227
2018	426
2017	153
2016	89
Prior	3
Net investment in sales-type leases	956	$ 1,600	$ 1,562
Payment Performance Performing [Member]
Sales Type Lease Net Investment In Lease Credit Quality Indicator [Line Items]
2020	58
2019	227
2018	426
2017	153
2016	89
Prior	3
Net investment in sales-type leases	$ 956

Current Expected Credit Losse_4

Current Expected Credit Losses - Available-for-Sale Debt Securities in Unrealized Loss Position (Detail) - USD ($) $ in Thousands	Sep. 30, 2020	Jan. 01, 2020
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	$ 4,864	$ 8,965
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(12)	(19)
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	4,864	9,101
Total Unrealized Losses	(12)	(21)
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value		203
Total Fair Value		203
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	394	930
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(1)
Total Fair Value	394	930
Total Unrealized Losses	(1)
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	396	797
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses		(3)
Total Fair Value	396	797
Total Unrealized Losses		(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	3,199	2,594
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses	(11)	(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	3,199	2,730
Total Unrealized Losses	(11)	(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	800	4,070
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses		(9)
Total Fair Value	800	4,070
Total Unrealized Losses		(9)
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Continuous Unrealized Loss Position for Less than 12 Months, Fair Value	75	371
Continuous Unrealized Loss Position for Less than 12 Months, Unrealized Losses		(1)
Total Fair Value	$ 75	371
Total Unrealized Losses		$ (1)

Restructuring - Schedule of Rec

Restructuring - Schedule of Reconciliation of Restructuring Liability (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Restructuring And Related Activities [Abstract]
Balance at beginning of period	$ 358		$ 1,568	$ 185	$ 185
Plus: Amounts charged to expense	1,903	$ 1,195	3,648	$ 4,658	6,014
Less: Amounts paid	(542)		(3,497)		(4,631)
Balance at end of period	$ 1,719		$ 1,719		$ 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		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 1,903	$ 1,195	$ 3,648	$ 4,658	$ 6,014
Selling, General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	1,050	531	1,622	2,078
Research and Development Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	621	602	1,738	1,833
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 232	$ 62	$ 288	$ 747

Restructuring - Schedule of C_2

Restructuring - Schedule of Components of Restructuring Expense by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 1,903	$ 1,195	$ 3,648	$ 4,658	$ 6,014
United States [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	448	1,116	2,191	1,941
International [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 1,455	$ 79	$ 1,457	$ 2,717

Restructuring - Additional Info

Restructuring - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2020USD ($)
Restructuring And Related Activities [Abstract]
Cumulative amount of restructuring expenses incurred for restructuring plan	$ 9.7

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($)	Nov. 04, 2020	Nov. 02, 2020	Sep. 30, 2020	Jun. 30, 2020	Mar. 31, 2020	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 01, 2020
Subsequent Event [Line Items]
Common stock dividends per share declared			$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09	$ 0.09
Scenario Forecast [Member]
Subsequent Event [Line Items]
Quarterly dividend payable, aggregate amount subsequent to balance sheet date									$ 4,300,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividend declaration date		Nov. 2, 2020
Common stock dividends per share declared		$ 0.09
Dividend record date		Nov. 17, 2020
Dividend payment date		Dec. 1, 2020
Subsequent Event [Member] | Cadence Bank, N.A [Member] | Secured Revolving Credit Facility [Member] | Revolving Credit and Security Agreement (The “Revolving Credit Agreement”) [Member]
Subsequent Event [Line Items]
Secured revolving credit facility amount	$ 10,000,000
Credit agreement maturity period	Nov. 4, 2021
Maximum loan to value ratio percentage	75.00%
Maximum interest rate in no event time	1.50%
Subsequent Event [Member] | Cadence Bank, N.A [Member] | Secured Revolving Credit Facility [Member] | Revolving Credit and Security Agreement (The “Revolving Credit Agreement”) [Member] | Screen Rate [Member]
Subsequent Event [Line Items]
Debt instrument interest over screen rate	1.50%