ADTRAN (ADTN) 10-Q 6 May 22 2022 Q1 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	3 Months Ended
	Mar. 31, 2022	May 04, 2022
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Mar. 31, 2022
Document Fiscal Year Focus	2022
Document Fiscal Period Focus	Q1
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		49,120,235
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	Mar. 31, 2022	Dec. 31, 2021
Current Assets
Cash and cash equivalents	$ 53,979	$ 56,603
Restricted cash	52	215
Short-term investments (includes $429 and $350 of available-for-sale securities as of March 31, 2022 and December 31, 2021, respectively, reported at fair value)	429	350
Accounts receivable, less allowance for credit losses of $0 as of March 31, 2022 and December 31, 2021	150,111	158,742
Other receivables	17,373	11,228
Inventory, net	171,121	139,891
Prepaid expenses and other current assets	9,076	9,296
Total Current Assets	402,141	376,325
Property, plant and equipment, net	54,384	55,766
Deferred tax assets, net	8,939	9,079
Goodwill	6,968	6,968
Intangibles, net	18,405	19,293
Other non-current assets	30,542	30,971
Long-term investments (includes $29,129 and $29,717 of available-for-sale securities as of March 31, 2022 and December 31, 2021, respectively, reported at fair value)	67,713	70,615
Total Assets	589,092	569,017
Current Liabilities
Accounts payable	127,111	102,489
Unearned revenue	19,454	17,737
Accrued expenses and other liabilities	18,736	13,673
Accrued wages and benefits	13,953	14,900
Income tax payable, net	3,519	6,560
Total Current Liabilities	182,773	155,359
Non-current unearned revenue	9,381	9,271
Pension liability	10,667	11,402
Deferred compensation liability	29,691	31,383
Other non-current liabilities	4,264	4,500
Total Liabilities	236,776	211,915
Commitments and contingencies (see Note 17)
Stockholders’ Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,652 shares issued and 49,133 shares outstanding as of March 31, 2022 and 79,652 shares issued and outstanding as of December 31, 2021	797	797
Additional paid-in capital	290,839	288,946
Accumulated other comprehensive loss	(13,556)	(11,914)
Retained earnings	734,249	740,820
Treasury stock at cost: 30,519 and 30,590 shares at March 31, 2022 and December 31,2021, respectively	(660,013)	(661,547)
Total Stockholders’ Equity	352,316	357,102
Total Liabilities and Stockholders’ Equity	$ 589,092	$ 569,017

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Statement of Financial Position [Abstract]
Short term investments, available-for-sale securities at fair value	$ 429	$ 350
Accounts receivable, allowance for expected credit losses	0	0
Long Term Investments, available-for-sale securities Fair Value	$ 29,129	$ 29,717
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	49,133,000	49,063,000
Treasury stock, shares	30,519,000	30,590,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of (Loss) Income (Unaudited) - USD ($) shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenue
Total Revenue	$ 154,518	$ 127,533
Cost of Revenue
Total Cost of Revenue	100,202	73,932
Gross Profit	54,316	53,601
Selling, general and administrative expenses	27,893	27,435
Research and development expenses	26,491	27,501
Operating Loss	(68)	(1,335)
Interest and dividend income	204	290
Interest expense	(30)	(6)
Net investment (loss) gain	(3,415)	996
Other (expense) income, net	(226)	1,999
(Loss) Income Before Income Taxes	(3,535)	1,944
Income tax benefit (expense)	2,408	(1,048)
Net (Loss) Income	$ (1,127)	$ 896
Weighted average shares outstanding – basic	49,113	48,336
Weighted average shares outstanding – diluted	49,113	49,004
(Loss) earnings per common share - basic	$ (0.02)	$ 0.02
(Loss) earnings per common share - diluted	$ (0.02)	$ 0.02
Network Solutions [Member]
Revenue
Total Revenue	$ 138,374	$ 113,809
Cost of Revenue
Total Cost of Revenue	90,653	65,001
Gross Profit	47,721	48,808
Services & Support [Member]
Revenue
Total Revenue	16,144	13,724
Cost of Revenue
Total Cost of Revenue	9,549	8,931
Gross Profit	$ 6,595	$ 4,793

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Comprehensive Income (Loss) (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Comprehensive Income [Abstract]
Net (Loss) Income	$ (1,127)	$ 896
Other Comprehensive (Loss) Income, net of tax
Net unrealized loss on available-for-sale securities	(724)	(192)
Defined benefit plan adjustments	(13)	99
Foreign currency translation loss	(905)	(1,863)
Other Comprehensive (Loss) Income, net of tax	(1,642)	(1,956)
Comprehensive Loss, net of tax	$ (2,769)	$ (1,060)

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid-In Capital [Member]	Retained Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Loss [Member]
Beginning Balance at Dec. 31, 2020	$ 372,944	$ 797	$ 281,466	$ 781,813	$ (679,493)	$ (11,639)
Beginning Balance, Shares at Dec. 31, 2020		79,652
Net Income (Loss)	896			896
Other comprehensive income (loss), net of tax	(1,956)					(1,956)
Dividend payments ($0.09 per share)	(4,361)			(4,361)
Dividends accrued on unvested RSUs	(68)			(68)
Deferred compensation adjustments, net of tax	(50)				(50)
PSUs, RSUs and restricted stock vested	(81)			(1,683)	1,602
Stock options exercised	1,244			(476)	1,720
Stock-based compensation expense	1,807		1,807
Ending Balance at Mar. 31, 2021	370,375	$ 797	283,273	776,121	(676,221)	(13,595)
Ending Balance, Shares at Mar. 31, 2021		79,652
Beginning Balance at Dec. 31, 2021	$ 357,102	$ 797	288,946	740,820	(661,547)	(11,914)
Beginning Balance, Shares at Dec. 31, 2021	79,652	79,652
Net Income (Loss)	$ (1,127)			(1,127)
Other comprehensive income (loss), net of tax	(1,642)					(1,642)
Dividend payments ($0.09 per share)	(4,438)			(4,438)
Dividends accrued on unvested RSUs	32			32
Deferred compensation adjustments, net of tax	(18)				(18)
PSUs, RSUs and restricted stock vested	(54)			(895)	841
Stock options exercised	568			(143)	711
Stock-based compensation expense	1,893		1,893
Ending Balance at Mar. 31, 2022	$ 352,316	$ 797	$ 290,839	$ 734,249	$ (660,013)	$ (13,556)
Ending Balance, Shares at Mar. 31, 2022	79,652	79,652

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Changes in Stockholders' Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Statement of Stockholders' Equity [Abstract]
Dividend payments	$ 0.09	$ 0.09

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Cash flows from operating activities:
Net (loss) income	$ (1,127)	$ 896
Adjustments to reconcile net (loss) income to net cash provided by operating activities:
Depreciation and amortization	3,661	4,122
Loss (gain) on investments	3,304	(1,161)
Stock-based compensation expense	1,893	1,807
Other, net	(62)	84
Inventory reserves	(1,754)	(2,131)
Changes in operating assets and liabilities:
Accounts receivable, net	8,697	(4,762)
Other receivables	(6,205)	(1,220)
Inventory	(29,685)	4,024
Prepaid expenses, other current assets and other assets	(1,170)	(417)
Accounts payable	24,818	5,629
Accrued expenses and other liabilities	3,803	3,317
Income taxes payable, net	(1,304)	497
Net cash provided by operating activities	4,869	10,685
Cash flows from investing activities:
Purchases of property, plant and equipment	(1,461)	(741)
Proceeds from sales and maturities of available-for-sale investments	10,265	10,087
Purchases of available-for-sale investments	(11,504)	(11,350)
Net cash used in investing activities	(2,700)	(2,004)
Cash flows from financing activities:
Tax withholdings related to stock-based compensation settlements	(54)	(113)
Proceeds from stock option exercises	568	1,244
Dividend payments	(4,438)	(4,361)
Proceeds from draw on line of credit	8,000
Repayment of line of credit	(8,000)
Net cash used in financing activities	(3,924)	(3,230)
Net (decrease) increase in cash, cash equivalents and restricted cash	(1,755)	5,451
Effect of exchange rate changes	(1,032)	(1,734)
Cash, cash equivalents and restricted cash, beginning of period	56,818	60,179
Cash, cash equivalents and restricted cash, end of period	54,031	63,896
Supplemental disclosure of non-cash investing activities:
Right-of-use assets obtained in exchange for lease obligations	332	248
Purchases of property, plant and equipment included in accounts payable	$ 392	$ 199

Summary of Significant Accounti

Summary of Significant Accounting Policies	3 Months Ended
	Mar. 31, 2022
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 ® , Inc. and its subsidiaries (“ADTRAN”, the “Company”, “we”, “our” or “us”) have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) applicable to interim financial information presented in Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by genera lly accepted accounting principles in the United States of America (“U.S. GAAP”) for complete financial statements are not included herein. Certain prior year amounts have been reclassified to conform to the current period presentation. The December 31, 2021 Condensed C onsolidated Balance Sheet is derived from audited financial statements but does not include all disclosures required by U.S. GAAP. 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, 2021 , filed with the SEC on February 25, 2022. 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. Significant estimates include excess and obsolete inventory reserves, warranty reserves, customer rebates, determination and accrual of the deferred revenue related to performance obligations under contracts with customers, 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 SARS-CoV-2 coronavirus/COVID-19 global pandemic (or variants of the SARS-CoV-2 coronavirus) as well as supply chain constraints as of March 31, 2022 and through the date of this report. The accounting matters assessed included, but were not limited to, the allowance for credit losses, stock-based compensation, carrying value of goodwill, intangibles and other long-lived assets, financial assets, valuation allowances for tax assets, revenue recognition and costs of revenue. Future conditions related to the magnitude and duration of the COVID-19 pandemic, as well as other factors, including supply chain constraints, could result in further impacts to our consolidated financial statements in future reporting periods. Recently Adopted Accounting Pronouncements There are currently no recently adopted accounting pronouncements that had a material effect on the condensed consolidated financial statements. Recent Accounting Pronouncements Not Yet Adopted In October 2021, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") 2021-08, Business Combinations (Topic 805) Accounting for Contract Assets and Contract Liabilities from Contracts with Customers, which would require an acquirer to recognize and measure acquired contract assets and contract liabilities in a manner consistent with how the acquiree recognized and measured them in its pre-acquisition financial statements in accordance with Topic 606, Revenue Recognition. ASU 2021-08 is effective for annual periods beginning after December 15, 2022, including interim periods within those fiscal years. Adoption of the ASU should be applied prospectively. Early adoption is also permitted, including adoption in an interim period. If early adopted, the amendments are applied retros pectively to all business combinations for which the acquisition date occurred during the fiscal year of adoption. The Company plans to early adopt ASU 2021-08 in the event that the Business Combination Agreement with ADVA closes during 2022. Ho wever, we are unable to estimate the effect on our Condensed Consolidated Financial Statements as of the date of this report.

Cash, Cash Equivalents and Rest

Cash, Cash Equivalents and Restricted Cash	3 Months Ended
	Mar. 31, 2022
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 Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statements of Cash Flows: As of As of (In thousands) March 31, 2022 December 31, 2021 Cash and cash equivalents $ 53,979 $ 56,603 Restricted cash 52 215 Cash, cash equivalents and restricted cash $ 54,031 $ 56,818 See Note 17 for additional information regarding restricted cash.

Revenue

Revenue	3 Months Ended
	Mar. 31, 2022
Revenue from Contract with Customer [Abstract]
Revenue	3. REVENUE The following is a description of the principal activities from which revenue is generated by reportable segment: Network Solutions Segment - Includes hardware products and software-defined next-generation virtualized solutions used in service provider or business networks, as well as prior generation products. Services & Support Segment - Includes maintenance, network implementation, solutions integration and managed services, which include hosted cloud services and subscription services. Revenue 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: Three Months Ended March 31, 2022 March 31, 2021 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Access & Aggregation $ 84,289 $ 11,171 $ 95,460 $ 60,053 $ 9,021 $ 69,074 Subscriber Solutions & Experience 51,823 2,783 54,606 52,269 2,300 54,569 Traditional & Other Products 2,262 2,190 4,452 1,487 2,403 3,890 Total $ 138,374 $ 16,144 $ 154,518 $ 113,809 $ 13,724 $ 127,533 The aggregate amount of transaction price allocated to remaining performance obligations that have not been satisfied as of March 31, 2022 and December 31, 2021 related to contractual maintenance agreements, contractual SaaS and subscription services, and hardware contracts that exceed one year in duration amounted to $ 133.1 million and $ 101.1 million, respectively. As of March 31, 2022, approximately 81.1 % is expected to be recognized over the next 12 months and the remainder recognized thereafter. The majority of the Company's remaining performance obligations at March 31, 2022 are related to contracts or orders that have an original expected duration of one year or less, for which the Company is electing to utilize the practical expedient available within the guidance, and are excluded from the transaction price related to these future obligations. The Company will generally satisfy the remaining performance obligations as we transfer control of the products ordered or services to our customers, excluding maintenance services, which are satisfied over time. The following table provides information about receivables, contract assets and unearned revenue from contracts with customers: As of As of (In thousands) March 31, 2022 December 31, 2021 Accounts receivable, net $ 150,111 $ 158,742 Contract assets (1) $ 8,243 $ 464 Unearned revenue $ 19,454 $ 17,737 Non-current unearned revenue $ 9,381 $ 9,271 (1) Included in other receivables on the Condensed Consolidated Balance Sheets. Of the outstanding unearned revenue balances as of December 31, 2021 , $ 5.4 million was recognized as revenue during the three months ended March 31, 2022 . Of the $ 14.1 million of outstanding unearned revenue balances as of December 31, 2020, $ 5.0 million was recognized as revenue during the three months ended March 31, 2021.

Income Taxes

Income Taxes	3 Months Ended
	Mar. 31, 2022
Income Tax Disclosure [Abstract]
Income Taxes	4. INCOME TAXES Our effective tax rate decreased from an expense of 53.9 % of pre-tax income for the three months ended March 31, 2021, to a benefit of 68.1 % of pre-tax loss for the three months ended March 31, 2022. The change in the effective tax rate for the three months ended March 31, 2022, was driven primarily by a change in our annual estimated tax rate as a result of the requirement to begin capitalizing research and development expenses for U.S. tax purposes beginning in 2022 as previously passed as part of the Tax Cuts and Jobs Act in December 2017 and the associated impact of those changes on our previously established valuation allowance. The Company continually reviews the adequacy of its valuation allowance and recognizes the benefits of deferred tax assets only as the assessment indicates that it is more likely than not that the deferred tax assets will be recognized in accordance with ASC 740, Income Taxes. As of March 31, 2022, the Company had deferred tax assets totaling $ 67.6 million, and a valuation allowance totaling $ 58.7 million against those deferred tax assets. The remaining $ 8.9 million in deferred tax assets not offset by a valuation allowance are located in various foreign jurisdictions where the Company believes it is more likely than not we will realize these deferred tax assets. During the three months ended March 31, 2022, the total change in the valuation allowance against our domestic and international deferred tax assets was recorded in the amount of an $ 8.2 million increase and a $ 0.1 million decrease, respectively. Our assessment of the realizability of our deferred tax assets includes the evaluation of historical operating results as well as the evaluation of evidence which requires significant judgment, including the evaluation of our three-year cumulative income position, future taxable income projections and tax planning strategies. Should management’s conclusion change in the future and an additional valuation allowance or a partial or full release of the valuation allowance becomes necessary, it may have a material effect on our consolidated financial statements. Supplemental balance sheet information related to deferred tax assets is as follows: As of March 31, 2022 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 56,460 $ ( 56,460 ) $ — International 11,121 ( 2,182 ) 8,939 Total $ 67,581 $ ( 58,642 ) $ 8,939 As of December 31, 2021 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 48,265 $ ( 48,265 ) $ — International 11,378 ( 2,299 ) 9,079 Total $ 59,643 $ ( 50,564 ) $ 9,079

Stock-Based Compensation

Stock-Based Compensation	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [Abstract]
Stock-Based Compensation	5. 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: Three Months Ended March 31, (In thousands) 2022 2021 Stock-based compensation expense included in cost of revenue $ 159 $ 131 Selling, general and administrative expense 1,124 1,098 Research and development expense 610 578 Stock-based compensation expense included in operating expenses 1,734 1,676 Total stock-based compensation expense 1,893 1,807 Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock ( 473 ) ( 431 ) Total stock-based compensation expense, net of tax $ 1,420 $ 1,376 PSUs, RSUs and Restricted Stock The following table summarizes PSUs, RSUs and restricted stock outstanding as of December 31, 2021 and March 31, 2022 and the changes that occurred during the three months ended March 31, 2022: Number of Weighted Avg. Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2021 1,930 $ 14.11 PSUs, RSUs and restricted stock granted 328 $ 20.21 PSUs, RSUs and restricted stock vested ( 10 ) $ 12.36 PSUs, RSUs and restricted stock forfeited ( 28 ) $ 13.72 Unvested PSUs, RSUs and restricted stock outstanding, March 31, 2022 2,220 $ 15.03 During each of the three months ended March 31, 2022 and 2021, the Company granted 0.3 million performance-based PSUs to its executive officers and certain employees. The grant-date fair value of these performance-based awards was based on the closing price of the Company’s stock on the date of grant. These awards vest over one-year , two-year and three-year periods, respectively, subject to the grantee’s continued employment, with the ability to earn shares in a range of 0 % to 142.8 % of the awarded number of PSUs based on the achievement of defined performance targets. Equity-based compensation expense with respect to these awards may be adjusted over the vesting period to reflect the probability of achievement of performance targets defined in the award agreements. 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 March 31, 2022 , total unrecognized compensation expense related to non-vested market-based PSUs, RSUs and restricted stock was approximately $ 15.9 million, which will be recognized over the remaining weighted-average period of 2.7 years. In addition, there was $ 13.2 million of unrecognized compensation expense related to unvested 2020, 2021 and 2022 performance-based PSUs, which will be recognized over the remaining requisite service period of 0.8 years if achievement of the performance obligation becomes probable. Unrecognized compensation expense will be adjusted for actual forfeitures. As of March 31, 2022 , 3.8 million shares were available for issuance under stockholder-approved equity plans. Stock Options The following table summarizes stock options outstanding as of December 31, 2021 and March 31, 2022 and the changes that occurred during the three months ended March 31, 2022: Number of Weighted Avg. Weighted Avg. Aggregate Stock options outstanding, December 31, 2021 1,721 $ 19.37 2.4 $ 6,669 Stock options exercised ( 33 ) $ 17.27 $ 101 Stock options expired ( 9 ) $ 23.18 $ 4 Stock options outstanding, March 31, 2022 1,679 $ 19.39 2.2 $ 1,758 Stock options exercisable, March 31, 2022 1,679 $ 19.39 2.2 $ 1,758 As of March 31, 2022 , there was no unrecognized compensation expense related to stock options as all awards vested in prior periods. There were no stock options granted during the three months ended March 31, 2022 and 2021. 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 March 31, 2022 . The amount of aggregate intrinsic value was $ 1.8 million as of March 31, 2022 and will change based on the fair market value of ADTRAN’s stock. The total pre-tax intrinsic value of options exercised during the three months ended March 31, 2022 was $ 0.1 million.

Investments

Investments	3 Months Ended
	Mar. 31, 2022
Investments, Debt and Equity Securities [Abstract]
Investments	6. INVESTMENTS Debt Securities and Other Investments The following debt securities and other investments were included on the Condensed Consolidated Balance Sheet and recorded at fair value: As of March 31, 2022 Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 9,299 $ 1 $ ( 206 ) $ 9,094 Municipal fixed-rate bonds 1,684 — ( 37 ) 1,647 Asset-backed bonds 318 — ( 11 ) 307 Mortgage/Agency-backed bonds 4,703 1 ( 142 ) 4,562 U.S. government bonds 14,000 — ( 446 ) 13,554 Foreign government bonds 411 — ( 17 ) 394 Available-for-sale debt securities held at fair value $ 30,415 $ 2 $ ( 859 ) $ 29,558 As of December 31, 2021 Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 10,776 $ 6 $ ( 35 ) $ 10,747 Municipal fixed-rate bonds 1,553 2 ( 4 ) 1,551 Asset-backed bonds 322 3 ( 3 ) 322 Mortgage/Agency-backed bonds 4,754 15 ( 33 ) 4,736 U.S. government bonds 12,251 12 ( 92 ) 12,171 Foreign government bonds 543 — ( 4 ) 539 Available-for-sale debt securities held at fair value $ 30,199 $ 38 $ ( 171 ) $ 30,066 The contractual maturities related to debt securities and other investments were as follows: As of March 31, 2022 (In thousands) Corporate Municipal Asset- Mortgage/ U.S. government Foreign government bonds Less than one year $ 295 $ 269 $ — $ 1,050 $ 979 $ — One to two years 5,965 1,265 — 479 4,800 — Two to three years 2,596 113 — 289 7,106 394 Three to five years 238 — 49 371 669 — Five to ten years — — — 915 — — More than ten years — — 258 1,458 — — Total $ 9,094 $ 1,647 $ 307 $ 4,562 $ 13,554 $ 394 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 the gross realized gains and losses related to our debt securities: Three Months Ended March 31, (In thousands) 2022 2021 Gross realized gain on debt securities $ 12 $ 87 Gross realized loss on debt securities ( 40 ) ( 16 ) Total (loss) gain recognized, net $ ( 28 ) $ 71 Income generated from available-for-sale debt securities was recorded as interest and dividend income in the Condensed Consolidated Statements of (Loss) Income. No allowance for credit losses was recorded for the three months ended March 31, 2022 and 2021 related to available-for-sale debt securities. The Company’s investment policy provides limitations for issuer concentration, which limits, at the time of purchase, the concentration in any one issuer to 5 % of the market value of our total investment portfolio. The Company did no t purchase any available-for-sale debt security with credit deterioration during the three months ended March 31, 2022. Marketable Equity Securities Our marketable equity securities consist of publicly traded stock, interests in funds and certain other investments measured at fair value or cost (where appropriate). The Company has an equity investment which does not have a readily determinable fair value, and is recorded 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 the equity investment as of March 31, 2022 and December 31, 2021 was $ 1.0 million. During the year ended December 31, 2021, impairment charges totaling $ 0.4 million, were recorded related to the equity investment. As of March 31 2022, cumulative impairment charges totaling $ 2.4 million were recorded related to the equity investment. There were no impairment charges during the three months ended March 31, 2022 and 2021. During the year ended December 31, 2021, an unsecured loan totaling $ 0.5 million was converted to equity which increased the Company's carrying value of the equity investment. The Company has a secured note receivable as of March 31, 2022 and December 31, 2021 which totaled $ 0.4 million and is included in long term investments on the Consolidated Balance Sheets. During the year ended December 31, 2021, an impairment charge of $ 0.5 million was recognized against the secured note receivable. There were no impairment charges during the three months ended March 31, 2022 and 2021. Realized and unrealized gains and losses related to marketable equity securities were as follows: Three Months Ended March 31, (In thousands) 2022 2021 Realized (loss) gain on equity securities sold $ ( 25 ) $ 24 Unrealized (loss) gain on equity securities held ( 3,362 ) 901 Total (loss) gain recognized, net $ ( 3,387 ) $ 925 Income generated from marketable equity securities was recorded as interest and dividend income in the Condensed Consolidated Statements of (Loss) Income. U.S. GAAP establishes a three-level valuation hierarchy based upon observable and unobservable inputs for fair value measurement of financial instruments: • Level 2 – Significant inputs that are observable; values based on quoted prices in markets that are not active or model inputs that are observable either directly or indirectly; • Level 3 – Significant unobservable inputs; values based on prices or valuation techniques that require inputs that are both unobservable and significant to the overall fair value measurement. These inputs could include information supplied by investees. The Company’s cash equivalents and investments held at fair value are categorized into this hierarchy as follows: Fair Value Measurements as of March 31, 2022 Using (In thousands) Fair Value Quoted Prices Significant Significant Unobservable Inputs Cash equivalents Money market funds $ 457 $ 457 $ — $ — Available-for-sale debt securities Corporate bonds 9,094 — 9,094 — Municipal fixed-rate bonds 1,647 — 1,647 — Asset-backed bonds 307 — 307 — Mortgage/Agency-backed bonds 4,562 — 4,562 — U.S. government bonds 13,554 13,554 — Foreign government securities 394 — 394 — Marketable equity securities Marketable equity securities – various industries 11,143 11,143 — — Deferred compensation plan assets 26,081 26,081 — — Total $ 67,239 $ 51,235 $ 16,004 $ — Fair Value Measurements as of December 31, 2021 Using (In thousands) Fair Value Quoted Prices Significant Significant Unobservable Inputs Cash equivalents Money market funds $ 652 $ 652 $ — $ — Available-for-sale debt securities Corporate bonds 10,747 — 10,747 — Municipal fixed-rate bonds 1,551 — 1,551 — Asset-backed bonds 322 — 322 — Mortgage/Agency-backed bonds 4,736 — 4,736 — U.S. government bonds 12,171 12,171 — — Foreign government bonds 539 — 539 — Marketable equity securities Marketable equity securities – various industries 12,606 12,606 — — Deferred compensation plan assets 26,935 26,935 — — Total $ 70,259 $ 52,364 $ 17,895 $ — 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. Inputs used in preparing the third-party valuation included the following assumptions, among others: estimated discount rates and fair market yields.

Inventory

Inventory	3 Months Ended
	Mar. 31, 2022
Inventory Disclosure [Abstract]
Inventory	7. INVENTORY Inventory consisted of the following: As of As of (In thousands) March 31, 2022 December 31, 2021 Raw materials $ 100,644 $ 74,709 Work in process 2,232 2,143 Finished goods 68,245 63,039 Total inventory, net $ 171,121 $ 139,891 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 considers historical usage, known trends, inventory age and market conditions. As of March 31, 2022 and December 31, 2021 , inventory reserves were $ 46.3 million and $ 44.6 million, respectively.

Property, Plant and Equipment

Property, Plant and Equipment	3 Months Ended
	Mar. 31, 2022
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	8. PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consisted of the following: As of As of (In thousands) March 31, 2022 December 31, 2021 Land $ 4,575 $ 4,575 Building and land improvements 35,667 35,578 Building 68,161 68,157 Furniture and fixtures 19,956 19,917 Computer hardware and software 73,440 72,274 Engineering and other equipment 134,438 134,771 Total property, plant and equipment 336,237 335,272 Less: accumulated depreciation ( 281,853 ) ( 279,506 ) Total property, plant and equipment, net $ 54,384 $ 55,766 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. No impairment charges were recognized during the three months ended March 31, 2022 and 2021. Depreciation expense was $ 2.8 million and $ 3.1 million for the three months ended March 31, 2022 and 2021 respectively, which is recorded in cost of revenue, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of (Loss) Income.

Goodwill

Goodwill	3 Months Ended
	Mar. 31, 2022
Goodwill Disclosure [Abstract]
Goodwill	9. GOODWILL Goodwill was $ 7.0 million as of March 31, 2022 and December 31, 2021 , of which $ 6.6 million and $ 0.4 million was allocated to our Network Solutions and Services & Support reportable segments, respectively. Goodwill represents the excess purchase price over the fair value of net assets acquired. We qualitatively assess the carrying value of goodwill each reporting period for events or circumstance changes that would more likely than not reduce the fair value of the reporting unit below its carrying amount. Based on our assessment of certain qualitative factors such as macro-economic conditions, industry and market considerations, costs factors and overall financial performance, management concluded that no such events or circumstance changes were identified that would suggest that the fair value of the goodwill was more likely than not greater than its carrying amount as of March 31, 2022. No impairment of goodwill was recorded during the three months ended March 31, 2022 and 2021 .

Intangible Assets

Intangible Assets	3 Months Ended
	Mar. 31, 2022
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible Assets	10. INTANGIBLE ASSETS Intangible assets consisted of the following: As of March 31, 2022 As of December 31, 2021 (In thousands) Gross Carrying Amount Accumulated Amortization Net Book Value Gross Carrying Amount Accumulated Amortization Net Book Value Customer relationships $ 20,677 $ ( 10,192 ) $ 10,485 $ 20,796 $ ( 9,906 ) $ 10,890 Developed technology 8,200 ( 3,967 ) 4,233 8,200 ( 3,683 ) 4,517 Licensed technology 5,900 ( 2,650 ) 3,250 5,900 ( 2,486 ) 3,414 Licensing agreements 560 ( 243 ) 317 560 ( 225 ) 335 Patents 500 ( 380 ) 120 500 ( 363 ) 137 Trade names 210 ( 210 ) — 210 ( 210 ) — Total $ 36,047 $ ( 17,642 ) $ 18,405 $ 36,166 $ ( 16,873 ) $ 19,293 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 first quarters of 2022 and 2021. As a result, no impairment test of long-lived assets was performed as of March 31, 2022 and 2021 , and no impairment losses of intangible assets were recorded during the three months ended March 31, 2022 and 2021. Amortization expense was $ 0.9 million and $ 1.0 million in each of the three months ended March 31, 2022 and 2021, respectively, and was included in cost of revenue, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of (Loss) Income. Estimated future amortization expense of intangible assets was as follows: As of (In thousands) March 31, 2022 2022 $ 2,601 2023 3,316 2024 3,224 2025 3,023 2026 1,986 Thereafter 4,255 Total $ 18,405

Leases

Leases	3 Months Ended
	Mar. 31, 2022
Leases [Abstract]
Leases	11. LEASES Net Investment in Sales-Type Leases We are the lessor in sales-type lease arrangements for network equipment, which consisted of the following: As of As of (In thousands) March 31, 2022 December 31, 2021 Current minimum lease payments receivable (1) $ 66 $ 92 Non-current minimum lease payments receivable (2) 1 4 Total minimum lease payments receivable 67 96 Less: Current unearned revenue (1) 50 70 Less: Non-current unearned revenue (2) — 1 Net investment in sales-type leases $ 17 $ 25 (1) Included in other receivables on the Condensed Consolidated Balance Sheets. (2) Included in other assets on the Condensed Consolidated Balance Sheets.

Cadence Revolving Credit Agreem

Cadence Revolving Credit Agreement	3 Months Ended
	Mar. 31, 2022
Debt Disclosure [Abstract]
Cadence Revolving Credit Agreement	12. CADENCE REVOLVING CREDIT AGREEMENT On November 2, 2021, the Company, as borrower, renewed its Revolving Credit and Security Agreement and related Promissory Note (together, the “Cadence Revolving Credit Agreement”) with Cadence Bank, N.A., as lender (the “Cadence Lender”). The Cadence Revolving Credit Agreement provides the Company with a $ 10.0 million secured revolving credit facility. Loans under the Cadence 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 Cadence Lender from time to time; provided, however, that in no event shall the applicable rate of interest under the Cadence 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 Cadence Revolving Credit Agreement, at a maximum loan-to-value ratio of 75 % determined by dividing the full commitment amount under the Cadence Revolving Credit Agreement on the date of testing, determined by the Cadence Lender each fiscal quarter, by the market value of the collateral. The Cadence Revolving C redit Agreement matures on November 3, 2022 , subject to earlier termination upon the concurrence of certain events of default. The Company entered into the Cadence Revolving Credit Agreement in order to increase the flexibility and management of its short-term liquidity. During the first quarter of 2022, the Company made draws totaling $ 8.0 million under the Cadence Revolving Credit Agreement all of which had been repaid as of March 31, 2022. The Company agreed to certain negative covenants that are customary for credit arrangements of this type, including, among other things, r estrictions on the Company’s ability to enter into mergers, acquisitions or other business combination transactions, grant liens or suffer a material adverse change in the condition or affairs (financial or otherwise) of the Company. As of March 31, 2022, the Company was in compliance with all contractual requirements under the Cadence Revolving Credit Agreement.

Stockholders' Equity

Stockholders' Equity	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Stockholders' Equity	13. STOCKHOLDERS’ EQUITY Stock Repurchase Program Since 1997, the Company’s Board of Directors has approved multiple share repurchase programs that have authorized repurchases of the Company's common stock, which are implemented through open market or private purchases from time to time as conditions warrant. During the three months ended March 31, 2022 , we did no t repurchase any shares of our common stock. As of March 31, 2022 , 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 (Loss) Income The following tables present the changes in accumulated other comprehensive (loss) income, net of tax, by component: Three Months Ended March 31, 2022 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of December 31, 2021 $ ( 552 ) $ ( 5,613 ) $ ( 6,134 ) $ 385 $ ( 11,914 ) Other comprehensive loss before ( 975 ) — ( 905 ) — ( 1,880 ) Amounts reclassified from accumulated other 251 ( 13 ) — — 238 Balance as of March 31, 2022 $ ( 1,276 ) $ ( 5,626 ) $ ( 7,039 ) $ 385 $ ( 13,556 ) Three Months Ended March 31, 2021 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of December 31, 2020 $ 32 $ ( 9,621 ) $ ( 2,435 ) $ 385 $ ( 11,639 ) Other comprehensive loss before ( 57 ) — ( 1,863 ) — ( 1,920 ) Amounts reclassified from accumulated other ( 135 ) 99 — — ( 36 ) Balance as of March 31, 2021 $ ( 160 ) $ ( 9,522 ) $ ( 4,298 ) $ 385 $ ( 13,595 ) The following tables present the details of reclassifications out of accumulated other comprehensive loss: Three Months Ended March 31, 2022 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized loss on sales of securities $ ( 330 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial gain 19 (1) Total reclassifications for the period, before tax ( 311 ) Tax benefit 73 Total reclassifications for the period, net of tax $ ( 238 ) (1) A part of the computation of net periodic pension cost, which is included in other (expense) income, net in the Condensed Consolidated Statements of (Loss) Income. Three Months Ended March 31, 2021 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized gain on sales of securities $ 178 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses ( 143 ) (1) Total reclassifications for the period, before tax 35 Tax benefit 1 Total reclassifications for the period, net of tax $ 36 (1) A part of the computation of net periodic pension cost, which is included in other (expense) income, net in the Condensed Consolidated Statements of (Loss) Income. The following tables present the tax effects related to the change in each component of other comprehensive (loss) income: Three Months Ended Three Months Ended March 31, 2022 March 31, 2021 (In thousands) Before-Tax Tax Net-of-Tax Before-Tax Tax Net-of-Tax Unrealized loss on available-for-sale $ ( 1,283 ) $ 308 $ ( 975 ) $ ( 75 ) $ 18 $ ( 57 ) Reclassification adjustment for amounts related to 330 ( 79 ) 251 ( 178 ) 43 ( 135 ) Reclassification adjustment for amounts related to ( 19 ) 6 ( 13 ) 143 ( 44 ) 99 Foreign currency translation adjustment ( 905 ) — ( 905 ) ( 1,863 ) — ( 1,863 ) Total Other Comprehensive (Loss) Income $ ( 1,877 ) $ 235 $ ( 1,642 ) $ ( 1,973 ) $ 17 $ ( 1,956 )

(Loss) Earnings Per Share

(Loss) Earnings Per Share	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
(Loss) Earnings Per Share	14. (LOSS) EARNINGS PER SHARE The calculation of basic and diluted (loss) earnings per share is as follows: Three Months Ended March 31, (In thousands, except per share amounts) 2022 2021 Numerator Net (loss) income $ ( 1,127 ) $ 896 Denominator Weighted average number of shares – basic 49,113 48,336 Effect of dilutive securities Stock options — 56 PSUs, RSUs and restricted stock — 612 Weighted average number of shares – diluted 49,113 49,004 (Loss) earnings per share – basic $ ( 0.02 ) $ 0.02 (Loss) earnings per share – diluted $ ( 0.02 ) $ 0.02 For the three months ended March 31, 2022 and 2021, five thousand and one thousand shares, respectively, of unvested PSUs, RSUs and restricted stock were excluded from the calculation of diluted earnings per share due to their anti-dilutive effect. For the three months ended March 31, 2022 and 2021, 0.1 million and 0.7 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 applicable period, making them anti-dilutive under the treasury stock method.

Segment Information

Segment Information	3 Months Ended
	Mar. 31, 2022
Segment Reporting [Abstract]
Segment Information	15. SEGMENT INFORMATION The chief operating decision maker regularly reviews the Company’s financial performance based on two reportable segments: (1) Network Solutions and (2) Services & Support. Network Solutions includes hardware and software products and next-generation virtualized solutions used in service provider or business networks, as well as prior-generation products. Services & Support includes a portfolio of maintenance, network installation and solution integration services, which include hosted cloud services and subscription services. The performance of these 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), net and income tax benefit (expense) 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 table presents information about the revenue and gross profit of our reportable segments: Three Months Ended March 31, 2022 March 31, 2021 (In thousands) Revenue Gross Profit Revenue Gross Profit Network Solutions $ 138,374 $ 47,721 $ 113,809 $ 48,808 Services & Support 16,144 6,595 13,724 4,793 Total $ 154,518 $ 54,316 $ 127,533 $ 53,601 Revenue 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 revenue information by category: Three Months Ended March 31, (In thousands) 2022 2021 Access & Aggregation $ 95,460 $ 69,074 Subscriber Solutions & Experience 54,606 54,569 Traditional & Other Products 4,452 3,890 Total $ 154,518 $ 127,533 Revenue by Geographic Area The following table presents revenue information by geographic area: Three Months Ended March 31, (In thousands) 2022 2021 United States $ 99,048 $ 86,485 United Kingdom 30,388 8,042 Germany 10,920 14,374 Other international 14,162 18,632 Total $ 154,518 $ 127,533

Liability for Warranty Returns

Liability for Warranty Returns	3 Months Ended
	Mar. 31, 2022
Product Warranties Disclosures [Abstract]
Liability for Warranty Returns	16. LIABILITY FOR WARRANTY RETURNS Our products generally include warranties of 90 days to five years for product defects. We accrue for warranty returns at the time of product shipment based on our historical return rate and 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. The increasing complexity of our products may 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 our actual experience relative to these factors be worse than our estimates, we will be required to record additional warranty expense. The liability for warranty obligations totaled $ 5.1 million and $ 5.4 million as of March 31, 2022 and December 31, 2021 , respectively, and is included in accrued expenses and other liabilities in the Condensed Consolidated Balance Sheets. During the three months ended March 31, 2021, we had a net reversal of prior provisions related to warranty expirations the impact of which is reflected in the table below. The warranty expense and write-off activity for the three months ended March 31, 2022 and 2021 is summarized as follows: Three Months Ended March 31, (In thousands) 2022 2021 Balance at beginning of period $ 5,403 $ 7,146 Plus: Amounts charged to cost and expenses 344 ( 231 ) Less: Deductions ( 604 ) ( 443 ) Balance at end of period $ 5,143 $ 6,472

Commitments and Contingencies

Commitments and Contingencies	3 Months Ended
	Mar. 31, 2022
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	17. COMMITMENTS AND CONTINGENCIES Shareholder Derivative Lawsuit On March 31, 2020, a shareholder derivative suit, captioned Johnson (Derivatively on behalf of ADTRAN) v. Stanton, et al., Case No. 5:20-cv-00447, was filed in the U.S. District Court for the Northern District of Alabama against two of the Company’s current executive officers, one of its former executive officers, and certain current and former members of its Board of Directors, alleging, among other things, that the defendants made or caused the Company to make 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 plaintiff in the shareholder derivative suit sent a demand letter dated June 29, 2021 to ADTRAN’s Board of Directors. The letter contains similar allegations to those made in the plaintiff’s filed complaint and in the now dismissed securities class action, and it demands, among other things, that the Board of Directors commence an investigation into the alleged wrongdoing. On December 10, 2021, after investigating the allegations in the plaintiff’s demand with the assistance of independent counsel, the independent members of the Board of Directors concluded that pursuing the claims asserted in the demand would not be in the Company's best interests and exercised their business judgment to refuse the demand. The plaintiff subsequently dismissed the case. On February 25, 2022, the Court entered an order on the parties’ joint stipulation dismissing the case without prejudice. 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 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. Business Combination Agreement On August 30, 2021 , the Company and ADVA, entered into a business combination agreement (the “Business Combination Agreement”), pursuant to which both companies agreed to combine their respective businesses and each become subsidiaries of a new holding company, Acorn HoldCo, a Delaware corporation and currently a wholly-owned direct subsidiary of the Company. Under the terms of the Business Combination Agreement, Acorn MergeCo, Inc., a newly formed Delaware corporation and wholly-owned direct subsidiary of Acorn HoldCo (“Merger Sub”), will merge with and into ADTRAN, with ADTRAN surviving the merger (the “Merger”) as a wholly-owned direct subsidiary of Acorn HoldCo. Pursuant to the Merger, each outstanding share of common stock of the Company will be converted into the right to receive one share of common stock of Acorn HoldCo. Acorn HoldCo has also made a public exchange offer to exchange each issued and outstanding no-par value bearer share of ADVA, pursuant to which each ADVA share tendered and accepted for exchange will be exchanged for 0.8244 shares of common stock of Acorn HoldCo (the “Exchange Offer”, and together with the Merger, the “Business Combination”). Upon completion of the Business Combination, and assuming that all of the outstanding ADVA shares are exchanged in the Exchange Offer, former ADTRAN stockholders and former ADVA shareholders will own approximately 54 % and 46 %, respectively, of the outstanding Acorn HoldCo shares. The Business Combination Agreement was unanimously approved by the Board of Directors of the Company and by the supervisory board and management board of ADVA. On January 6, 2022, the Company's stockholders approved the Business Combination by an overwhelming majority. The end of the ADVA shareholder tender offer acceptance period was on January 26, 2022, which resulted in the acceptance of the Exchange Offer by more than 60 % of all shares of ADVA entitled to voting rights existing as of October 31, 2021, thus exceeding the required minimum acceptance threshold. According to the rules of the German Securities Acquisition and Takeover Act, ADVA shareholders who did not tender their shares during the initial acceptance period could do so during a two-week additional acceptance period that began on February 1, 2022 and ended February 14, 2022. This resulted in the acceptance of the Exchange Offer by approximately 66 % of all shares of ADVA entitled to voting rights existing as of November 30, 2021. On January 24, 2022, the Committee on Foreign Investment in the U.S. ("CFIUS") completed its review of the Business Combination and determined that the transaction was not a “covered transaction” subject to CFIUS’ jurisdiction, satisfying the condition of the Business Combination Agreement related to CFIUS notification. On February 16, 2022, the U.K. Secretary of State for Business, Energy and Industrial Strategy completed its review of the Business Combination and determined that the Secretary of State will be taking no further action under the NS&I Act, satisfying the condition of the Business Combination Agreement related to NS&I Act approval. Cooperative proceedings continue with the foreign direct investment authorities in Germany. The Company anticipates the consummation of the Business Combination around the middle of 2022, subject to customary closing conditions, and regul atory approvals from the foreign direct investment authorities in Germany. Additional information about the Business Combination Agreement and proposed Business Combination is set forth in the Company’s filings with the SEC, as well as in the registration statement on Form S-4 that Acorn HoldCo filed with the SEC, which was declared effective December 2, 2021 (the “Acorn HoldCo Registration Statement”). Performance Bonds C ertain 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 March 31, 2022 and December 31, 2021 , we had commitments related to these bonds totaling $ 20.9 million and $ 22.9 million, respectively, which expire at various dates through April 2025 . 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 this customer contract will be performed over multiple years. We reached the maximum value of our minimum collateral requirement of $ 15.0 million during the three months ended March 31, 2021 as the Company reached certain milestones through the first quarter of 2021 as outlined in the customer contract. The letter of credit was secured by a pledge of a portion of the Company’s fixed-income securities, which totaled $ 18.0 million as of March 31, 2022, of which $ 0.1 million is included in restricted cash and $ 17.9 million is included in long-term investments on the Condensed Consolidated Balance Sheets. This pledged collateral value will fluctuate as the Company changes the mix of the pledged collateral between restricted cash and investments. Any shortfalls in the minimum collateral value are required to be restored by the Company from available cash and cash equivalents, short-term investments 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 March 31, 2022, the Company believes it 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 invested as of March 31, 2022 .

Restructuring

Restructuring	3 Months Ended
	Mar. 31, 2022
Restructuring and Related Activities [Abstract]
Restructuring	18. RESTRUCTURING During the second half of 2019, the Company initiated a restructuring plan to realign its expense structure with the reduction in revenue experienced in recent years and overall Company objectives. As part of this restructuring plan, the Company announced plans to reduce its overall operating expenses, both in the U.S. and internationally. Management continued to assess the efficiency of operations during 2020 and the first three months of 2021 and, in turn, consolidated locations and personnel, among other things, where possible. 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. The cumulative amount of restructuring expenses incurred as of March 31, 2022 for the restructuring plans was $ 12.7 million. A reconciliation of the beginning and ending restructuring liability, which is included in accrued wages and benefits in the Condensed Consolidated Balance Sheets is as follows: Three Months Ended (In thousands) March 31, 2022 Balance as of December 31, 2021 $ 1,514 Plus: Amounts charged to cost and expense 2 Less: Amounts paid ( 1,256 ) Balance as of March 31, 2022 $ 260 (In thousands) For the Year Ended December 31, 2021 Balance as of December 31, 2020 $ 4,186 Plus: Amounts charged to cost and expense 411 Less: Amounts paid ( 3,083 ) Balance as of December 31, 2021 $ 1,514 Restructuring expenses included in the Condensed Consolidated Statements of (Loss) Income were as follows: Three Months Ended March 31, (In thousands) 2022 2021 Network Solutions - Cost of revenue $ — $ 12 Services & Support - Cost of revenue — 3 Cost of revenue $ — $ 15 Selling, general and administrative expenses (1) 2 142 Research and development expenses (1) — 144 Total restructuring expenses $ 2 $ 301 (1) The Company does not allocate selling, general and administrative expense and research and development expense to the segment level. Components of restructuring expense by geographic area were as follows: Three Months Ended March 31, (In thousands) 2022 2021 United States $ 2 $ 209 International — 92 Total restructuring expenses $ 2 $ 301

Subsequent Events

Subsequent Events	3 Months Ended
	Mar. 31, 2022
Subsequent Events [Abstract]
Subsequent Events	19. SUBSEQUENT EVENTS On May 4, 2022 , we announced that our Board of Directors declared a quarterly cash dividend of $ 0.09 per common share to be paid to the Company’s stockholders of record as of the close of business on May 19, 2022 . The payment date will be June 2, 2022 in the aggregate amount of approximately $ 4.4 million. On April 1, 2022, the Company entered into a Credit Agreement and related Revolving Line of Credit Note (together, the “Wells Revolving Credit Agreement”) in favor of Wells Fargo Bank, National Association, as lender (the “Wells Lender”). The Wells Revolving Credit Agreement provides the Company with a new $ 25 million secured revolving credit facility. The Wells Revolving Credit Agreement matures on April 1, 2023 , subject to earlier termination upon the occurrence of certain events of default as set forth in the Wells Revolving Credit Agreement. Loans under the Wells Revolving Credit Agreement will bear interest at a fluctuating rate per annum equal to: (i) the Daily Simple SOFR (as defined herein) plus (ii) an applicable margin, which will equal 1.00 %, 1.25 %, 1.5 % or 2.0 % per annum depending on the Company’s senior funded debt to EBITDA ratio. The “Daily Simple SOFR” is calculated based upon the greater of (x) a floor of 0.00 % and (b) the Secured Overnight Financing Rate, as established by the Federal Reserve Bank of New York (or a successor thereto) from time to time. Accrued interest is payable on the last day of each quarter, commencing June 30, 2022. Borrowings under the Wells Revolving Credit Agreement may be used solely for issuing letters of credit, financing capital expenditures, and working capital and general corporate purposes. Loans under the Wells Revolving Credit Agreement are secured by a first priority security interest in all of the accounts receivable of the Company and its subsidiary, ADTRAN International, Inc. Specifically, in connection with the Wells Revolving Credit Agreement, the Company entered into a security agreement, dated April 1, 2022, pursuant to which the Company pledged to the Wells Lender all of the rights to payment, accounts, deposit accounts, chattel paper (whether electronic or tangible), instruments, promissory notes, documents, licenses, general intangibles, payment intangibles, software, letter of credit rights and healthcare insurance receivables existing as of the date of execution or arising at any time thereafter.

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	3 Months Ended
	Mar. 31, 2022
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited condensed consolidated financial statements of ADTRAN ® , Inc. and its subsidiaries (“ADTRAN”, the “Company”, “we”, “our” or “us”) have been prepared pursuant to the rules and regulations of the Securities and Exchange Commission (the “SEC”) applicable to interim financial information presented in Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by genera lly accepted accounting principles in the United States of America (“U.S. GAAP”) for complete financial statements are not included herein. Certain prior year amounts have been reclassified to conform to the current period presentation. The December 31, 2021 Condensed C onsolidated Balance Sheet is derived from audited financial statements but does not include all disclosures required by U.S. GAAP. 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, 2021 , filed with the SEC on February 25, 2022.
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. Significant estimates include excess and obsolete inventory reserves, warranty reserves, customer rebates, determination and accrual of the deferred revenue related to performance obligations under contracts with customers, 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 SARS-CoV-2 coronavirus/COVID-19 global pandemic (or variants of the SARS-CoV-2 coronavirus) as well as supply chain constraints as of March 31, 2022 and through the date of this report. The accounting matters assessed included, but were not limited to, the allowance for credit losses, stock-based compensation, carrying value of goodwill, intangibles and other long-lived assets, financial assets, valuation allowances for tax assets, revenue recognition and costs of revenue. Future conditions related to the magnitude and duration of the COVID-19 pandemic, as well as other factors, including supply chain constraints, could result in further impacts to our consolidated financial statements in future reporting periods.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements There are currently no recently adopted accounting pronouncements that had a material effect on the condensed consolidated financial statements.
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In October 2021, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") 2021-08, Business Combinations (Topic 805) Accounting for Contract Assets and Contract Liabilities from Contracts with Customers, which would require an acquirer to recognize and measure acquired contract assets and contract liabilities in a manner consistent with how the acquiree recognized and measured them in its pre-acquisition financial statements in accordance with Topic 606, Revenue Recognition. ASU 2021-08 is effective for annual periods beginning after December 15, 2022, including interim periods within those fiscal years. Adoption of the ASU should be applied prospectively. Early adoption is also permitted, including adoption in an interim period. If early adopted, the amendments are applied retros pectively to all business combinations for which the acquisition date occurred during the fiscal year of adoption. The Company plans to early adopt ASU 2021-08 in the event that the Business Combination Agreement with ADVA closes during 2022. Ho wever, we are unable to estimate the effect on our Condensed Consolidated Financial Statements as of the date of this report.

Cash, Cash Equivalents and Re_2

Cash, Cash Equivalents and Restricted Cash (Tables)	3 Months Ended
	Mar. 31, 2022
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 Sheets that sum to the total of the same such amounts shown in the Condensed Consolidated Statements of Cash Flows: As of As of (In thousands) March 31, 2022 December 31, 2021 Cash and cash equivalents $ 53,979 $ 56,603 Restricted cash 52 215 Cash, cash equivalents and restricted cash $ 54,031 $ 56,818

Revenue (Tables)

Revenue (Tables)	3 Months Ended
	Mar. 31, 2022
Revenue from Contract with Customer [Abstract]
Disaggregate of Revenue by Reportable Segment and Revenue Category	The table below presents revenue information by category: Three Months Ended March 31, (In thousands) 2022 2021 Access & Aggregation $ 95,460 $ 69,074 Subscriber Solutions & Experience 54,606 54,569 Traditional & Other Products 4,452 3,890 Total $ 154,518 $ 127,533
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: As of As of (In thousands) March 31, 2022 December 31, 2021 Accounts receivable, net $ 150,111 $ 158,742 Contract assets (1) $ 8,243 $ 464 Unearned revenue $ 19,454 $ 17,737 Non-current unearned revenue $ 9,381 $ 9,271 (1) Included in other receivables on the Condensed Consolidated Balance Sheets.

Income Taxes (Tables)

Income Taxes (Tables)	3 Months Ended
	Mar. 31, 2022
Income Tax Disclosure [Abstract]
Summary of Supplemental Balance Sheet Information Related to Deferred Tax Assets	Supplemental balance sheet information related to deferred tax assets is as follows: As of March 31, 2022 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 56,460 $ ( 56,460 ) $ — International 11,121 ( 2,182 ) 8,939 Total $ 67,581 $ ( 58,642 ) $ 8,939 As of December 31, 2021 (In thousands) Deferred Tax Assets Valuation Allowance Deferred Tax Assets, net Domestic $ 48,265 $ ( 48,265 ) $ — International 11,378 ( 2,299 ) 9,079 Total $ 59,643 $ ( 50,564 ) $ 9,079

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	3 Months Ended
	Mar. 31, 2022
Share-based Payment Arrangement [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: Three Months Ended March 31, (In thousands) 2022 2021 Stock-based compensation expense included in cost of revenue $ 159 $ 131 Selling, general and administrative expense 1,124 1,098 Research and development expense 610 578 Stock-based compensation expense included in operating expenses 1,734 1,676 Total stock-based compensation expense 1,893 1,807 Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock ( 473 ) ( 431 ) Total stock-based compensation expense, net of tax $ 1,420 $ 1,376
Summary of PSUs, RSUs and Restricted Stock Outstanding	The following table summarizes PSUs, RSUs and restricted stock outstanding as of December 31, 2021 and March 31, 2022 and the changes that occurred during the three months ended March 31, 2022: Number of Weighted Avg. Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2021 1,930 $ 14.11 PSUs, RSUs and restricted stock granted 328 $ 20.21 PSUs, RSUs and restricted stock vested ( 10 ) $ 12.36 PSUs, RSUs and restricted stock forfeited ( 28 ) $ 13.72 Unvested PSUs, RSUs and restricted stock outstanding, March 31, 2022 2,220 $ 15.03
Summary of Stock Options Outstanding	The following table summarizes stock options outstanding as of December 31, 2021 and March 31, 2022 and the changes that occurred during the three months ended March 31, 2022: Number of Weighted Avg. Weighted Avg. Aggregate Stock options outstanding, December 31, 2021 1,721 $ 19.37 2.4 $ 6,669 Stock options exercised ( 33 ) $ 17.27 $ 101 Stock options expired ( 9 ) $ 23.18 $ 4 Stock options outstanding, March 31, 2022 1,679 $ 19.39 2.2 $ 1,758 Stock options exercisable, March 31, 2022 1,679 $ 19.39 2.2 $ 1,758

Investments (Tables)

Investments (Tables)	3 Months Ended
	Mar. 31, 2022
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 The following debt securities and other investments were included on the Condensed Consolidated Balance Sheet and recorded at fair value: As of March 31, 2022 Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 9,299 $ 1 $ ( 206 ) $ 9,094 Municipal fixed-rate bonds 1,684 — ( 37 ) 1,647 Asset-backed bonds 318 — ( 11 ) 307 Mortgage/Agency-backed bonds 4,703 1 ( 142 ) 4,562 U.S. government bonds 14,000 — ( 446 ) 13,554 Foreign government bonds 411 — ( 17 ) 394 Available-for-sale debt securities held at fair value $ 30,415 $ 2 $ ( 859 ) $ 29,558 As of December 31, 2021 Amortized Gross Unrealized Fair (In thousands) Cost Gains Losses Value Corporate bonds $ 10,776 $ 6 $ ( 35 ) $ 10,747 Municipal fixed-rate bonds 1,553 2 ( 4 ) 1,551 Asset-backed bonds 322 3 ( 3 ) 322 Mortgage/Agency-backed bonds 4,754 15 ( 33 ) 4,736 U.S. government bonds 12,251 12 ( 92 ) 12,171 Foreign government bonds 543 — ( 4 ) 539 Available-for-sale debt securities held at fair value $ 30,199 $ 38 $ ( 171 ) $ 30,066
Contractual Maturities of Debt Securities and Other Investments	The contractual maturities related to debt securities and other investments were as follows: As of March 31, 2022 (In thousands) Corporate Municipal Asset- Mortgage/ U.S. government Foreign government bonds Less than one year $ 295 $ 269 $ — $ 1,050 $ 979 $ — One to two years 5,965 1,265 — 479 4,800 — Two to three years 2,596 113 — 289 7,106 394 Three to five years 238 — 49 371 669 — Five to ten years — — — 915 — — More than ten years — — 258 1,458 — — Total $ 9,094 $ 1,647 $ 307 $ 4,562 $ 13,554 $ 394
Gross Realized Gains and Losses on Sale of Debt Securities	The following table presents the gross realized gains and losses related to our debt securities: Three Months Ended March 31, (In thousands) 2022 2021 Gross realized gain on debt securities $ 12 $ 87 Gross realized loss on debt securities ( 40 ) ( 16 ) Total (loss) gain recognized, net $ ( 28 ) $ 71
Realized and Unrealized Gains and Losses related to Marketable Equity Securities	Realized and unrealized gains and losses related to marketable equity securities were as follows: Three Months Ended March 31, (In thousands) 2022 2021 Realized (loss) gain on equity securities sold $ ( 25 ) $ 24 Unrealized (loss) gain on equity securities held ( 3,362 ) 901 Total (loss) gain recognized, net $ ( 3,387 ) $ 925
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 March 31, 2022 Using (In thousands) Fair Value Quoted Prices Significant Significant Unobservable Inputs Cash equivalents Money market funds $ 457 $ 457 $ — $ — Available-for-sale debt securities Corporate bonds 9,094 — 9,094 — Municipal fixed-rate bonds 1,647 — 1,647 — Asset-backed bonds 307 — 307 — Mortgage/Agency-backed bonds 4,562 — 4,562 — U.S. government bonds 13,554 13,554 — Foreign government securities 394 — 394 — Marketable equity securities Marketable equity securities – various industries 11,143 11,143 — — Deferred compensation plan assets 26,081 26,081 — — Total $ 67,239 $ 51,235 $ 16,004 $ — Fair Value Measurements as of December 31, 2021 Using (In thousands) Fair Value Quoted Prices Significant Significant Unobservable Inputs Cash equivalents Money market funds $ 652 $ 652 $ — $ — Available-for-sale debt securities Corporate bonds 10,747 — 10,747 — Municipal fixed-rate bonds 1,551 — 1,551 — Asset-backed bonds 322 — 322 — Mortgage/Agency-backed bonds 4,736 — 4,736 — U.S. government bonds 12,171 12,171 — — Foreign government bonds 539 — 539 — Marketable equity securities Marketable equity securities – various industries 12,606 12,606 — — Deferred compensation plan assets 26,935 26,935 — — Total $ 70,259 $ 52,364 $ 17,895 $ —

Inventory (Tables)

Inventory (Tables)	3 Months Ended
	Mar. 31, 2022
Inventory Disclosure [Abstract]
Components of Inventory	Inventory consisted of the following: As of As of (In thousands) March 31, 2022 December 31, 2021 Raw materials $ 100,644 $ 74,709 Work in process 2,232 2,143 Finished goods 68,245 63,039 Total inventory, net $ 171,121 $ 139,891

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	3 Months Ended
	Mar. 31, 2022
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment consisted of the following: As of As of (In thousands) March 31, 2022 December 31, 2021 Land $ 4,575 $ 4,575 Building and land improvements 35,667 35,578 Building 68,161 68,157 Furniture and fixtures 19,956 19,917 Computer hardware and software 73,440 72,274 Engineering and other equipment 134,438 134,771 Total property, plant and equipment 336,237 335,272 Less: accumulated depreciation ( 281,853 ) ( 279,506 ) Total property, plant and equipment, net $ 54,384 $ 55,766

Intangible Assets (Tables)

Intangible Assets (Tables)	3 Months Ended
	Mar. 31, 2022
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Summary of Intangible Assets	Intangible assets consisted of the following: As of March 31, 2022 As of December 31, 2021 (In thousands) Gross Carrying Amount Accumulated Amortization Net Book Value Gross Carrying Amount Accumulated Amortization Net Book Value Customer relationships $ 20,677 $ ( 10,192 ) $ 10,485 $ 20,796 $ ( 9,906 ) $ 10,890 Developed technology 8,200 ( 3,967 ) 4,233 8,200 ( 3,683 ) 4,517 Licensed technology 5,900 ( 2,650 ) 3,250 5,900 ( 2,486 ) 3,414 Licensing agreements 560 ( 243 ) 317 560 ( 225 ) 335 Patents 500 ( 380 ) 120 500 ( 363 ) 137 Trade names 210 ( 210 ) — 210 ( 210 ) — Total $ 36,047 $ ( 17,642 ) $ 18,405 $ 36,166 $ ( 16,873 ) $ 19,293
Estimated Future Amortization Expense Related to Intangible Assets	Estimated future amortization expense of intangible assets was as follows: As of (In thousands) March 31, 2022 2022 $ 2,601 2023 3,316 2024 3,224 2025 3,023 2026 1,986 Thereafter 4,255 Total $ 18,405

Leases (Tables)

Leases (Tables)	3 Months Ended
	Mar. 31, 2022
Leases [Abstract]
Net Investment in Sales-Type Leases	We are the lessor in sales-type lease arrangements for network equipment, which consisted of the following: As of As of (In thousands) March 31, 2022 December 31, 2021 Current minimum lease payments receivable (1) $ 66 $ 92 Non-current minimum lease payments receivable (2) 1 4 Total minimum lease payments receivable 67 96 Less: Current unearned revenue (1) 50 70 Less: Non-current unearned revenue (2) — 1 Net investment in sales-type leases $ 17 $ 25 (1) Included in other receivables on the Condensed Consolidated Balance Sheets. (2) Included in other assets on the Condensed Consolidated Balance Sheets.

Stockholders' Equity (Tables)

Stockholders' Equity (Tables)	3 Months Ended
	Mar. 31, 2022
Equity [Abstract]
Changes in Accumulated Other Comprehensive Loss, Net of Tax by Component	The following tables present the changes in accumulated other comprehensive (loss) income, net of tax, by component: Three Months Ended March 31, 2022 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of December 31, 2021 $ ( 552 ) $ ( 5,613 ) $ ( 6,134 ) $ 385 $ ( 11,914 ) Other comprehensive loss before ( 975 ) — ( 905 ) — ( 1,880 ) Amounts reclassified from accumulated other 251 ( 13 ) — — 238 Balance as of March 31, 2022 $ ( 1,276 ) $ ( 5,626 ) $ ( 7,039 ) $ 385 $ ( 13,556 ) Three Months Ended March 31, 2021 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of December 31, 2020 $ 32 $ ( 9,621 ) $ ( 2,435 ) $ 385 $ ( 11,639 ) Other comprehensive loss before ( 57 ) — ( 1,863 ) — ( 1,920 ) Amounts reclassified from accumulated other ( 135 ) 99 — — ( 36 ) Balance as of March 31, 2021 $ ( 160 ) $ ( 9,522 ) $ ( 4,298 ) $ 385 $ ( 13,595 )
Reclassifications Out of Accumulated Other Comprehensive Income (Loss)	The following tables present the details of reclassifications out of accumulated other comprehensive loss: Three Months Ended March 31, 2022 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized loss on sales of securities $ ( 330 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial gain 19 (1) Total reclassifications for the period, before tax ( 311 ) Tax benefit 73 Total reclassifications for the period, net of tax $ ( 238 ) (1) A part of the computation of net periodic pension cost, which is included in other (expense) income, net in the Condensed Consolidated Statements of (Loss) Income. Three Months Ended March 31, 2021 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized gain on sales of securities $ 178 Net investment gain (loss) Defined benefit plan adjustments – actuarial losses ( 143 ) (1) Total reclassifications for the period, before tax 35 Tax benefit 1 Total reclassifications for the period, net of tax $ 36 (1) A part of the computation of net periodic pension cost, which is included in other (expense) income, net in the Condensed Consolidated Statements of (Loss) Income.
Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Loss)	The following tables present the tax effects related to the change in each component of other comprehensive (loss) income: Three Months Ended Three Months Ended March 31, 2022 March 31, 2021 (In thousands) Before-Tax Tax Net-of-Tax Before-Tax Tax Net-of-Tax Unrealized loss on available-for-sale $ ( 1,283 ) $ 308 $ ( 975 ) $ ( 75 ) $ 18 $ ( 57 ) Reclassification adjustment for amounts related to 330 ( 79 ) 251 ( 178 ) 43 ( 135 ) Reclassification adjustment for amounts related to ( 19 ) 6 ( 13 ) 143 ( 44 ) 99 Foreign currency translation adjustment ( 905 ) — ( 905 ) ( 1,863 ) — ( 1,863 ) Total Other Comprehensive (Loss) Income $ ( 1,877 ) $ 235 $ ( 1,642 ) $ ( 1,973 ) $ 17 $ ( 1,956 )

(Loss) Earnings Per Share (Tabl

(Loss) Earnings Per Share (Tables)	3 Months Ended
	Mar. 31, 2022
Earnings Per Share [Abstract]
Summary of Calculation of Basic and Diluted Earnings (Loss) Per Share	The calculation of basic and diluted (loss) earnings per share is as follows: Three Months Ended March 31, (In thousands, except per share amounts) 2022 2021 Numerator Net (loss) income $ ( 1,127 ) $ 896 Denominator Weighted average number of shares – basic 49,113 48,336 Effect of dilutive securities Stock options — 56 PSUs, RSUs and restricted stock — 612 Weighted average number of shares – diluted 49,113 49,004 (Loss) earnings per share – basic $ ( 0.02 ) $ 0.02 (Loss) earnings per share – diluted $ ( 0.02 ) $ 0.02

Segment Information (Tables)

Segment Information (Tables)	3 Months Ended
	Mar. 31, 2022
Segment Reporting [Abstract]
Revenue and Gross Profit of Reportable Segments	The following table presents information about the revenue and gross profit of our reportable segments: Three Months Ended March 31, 2022 March 31, 2021 (In thousands) Revenue Gross Profit Revenue Gross Profit Network Solutions $ 138,374 $ 47,721 $ 113,809 $ 48,808 Services & Support 16,144 6,595 13,724 4,793 Total $ 154,518 $ 54,316 $ 127,533 $ 53,601
Disaggregate of Revenue by Reportable Segment and Revenue Category	The table below presents revenue information by category: Three Months Ended March 31, (In thousands) 2022 2021 Access & Aggregation $ 95,460 $ 69,074 Subscriber Solutions & Experience 54,606 54,569 Traditional & Other Products 4,452 3,890 Total $ 154,518 $ 127,533
Revenue Information by Geographic Area	The following table presents revenue information by geographic area: Three Months Ended March 31, (In thousands) 2022 2021 United States $ 99,048 $ 86,485 United Kingdom 30,388 8,042 Germany 10,920 14,374 Other international 14,162 18,632 Total $ 154,518 $ 127,533

Liability for Warranty Returns

Liability for Warranty Returns (Tables)	3 Months Ended
	Mar. 31, 2022
Product Warranties Disclosures [Abstract]
Summary of Warranty Expense and Write-off Activity	The warranty expense and write-off activity for the three months ended March 31, 2022 and 2021 is summarized as follows: Three Months Ended March 31, (In thousands) 2022 2021 Balance at beginning of period $ 5,403 $ 7,146 Plus: Amounts charged to cost and expenses 344 ( 231 ) Less: Deductions ( 604 ) ( 443 ) Balance at end of period $ 5,143 $ 6,472

Restructuring (Tables)

Restructuring (Tables)	3 Months Ended
	Mar. 31, 2022
Restructuring and Related Activities [Abstract]
Schedule of Reconciliation of Restructuring Liability	A reconciliation of the beginning and ending restructuring liability, which is included in accrued wages and benefits in the Condensed Consolidated Balance Sheets is as follows: Three Months Ended (In thousands) March 31, 2022 Balance as of December 31, 2021 $ 1,514 Plus: Amounts charged to cost and expense 2 Less: Amounts paid ( 1,256 ) Balance as of March 31, 2022 $ 260 (In thousands) For the Year Ended December 31, 2021 Balance as of December 31, 2020 $ 4,186 Plus: Amounts charged to cost and expense 411 Less: Amounts paid ( 3,083 ) Balance as of December 31, 2021 $ 1,514
Schedule of Components of Restructuring Expenses	Restructuring expenses included in the Condensed Consolidated Statements of (Loss) Income were as follows: Three Months Ended March 31, (In thousands) 2022 2021 Network Solutions - Cost of revenue $ — $ 12 Services & Support - Cost of revenue — 3 Cost of revenue $ — $ 15 Selling, general and administrative expenses (1) 2 142 Research and development expenses (1) — 144 Total restructuring expenses $ 2 $ 301 (1) The Company does not allocate selling, general and administrative expense and research and development expense to the segment level. Components of restructuring expense by geographic area were as follows: Three Months Ended March 31, (In thousands) 2022 2021 United States $ 2 $ 209 International — 92 Total restructuring expenses $ 2 $ 301

Cash, Cash Equivalents and Re_3

Cash, Cash Equivalents and Restricted Cash - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Cash and Cash Equivalents [Abstract]
Cash and cash equivalents	$ 53,979	$ 56,603
Restricted cash	52	215
Cash, cash equivalents and restricted cash	$ 54,031	$ 56,818

Revenue - Additional Informatio

Revenue - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)Category	Mar. 31, 2021USD ($)	Dec. 31, 2021USD ($)	Dec. 31, 2020USD ($)
Revenue [Line Items]
Number of categories | Category	3
Recognized revenue	$ 5.4	$ 5
Outstanding unearned revenue				$ 14.1
Contractual Maintenance Agreements, Contractual SaaS and Subscription Services and Hardware Contracts [Member]
Revenue [Line Items]
Remaining performance obligations	$ 133.1		$ 101.1

Revenue - Disaggregate of Reven

Revenue - Disaggregate of Revenue by Reportable Segment and Revenue Category (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation Of Revenue [Line Items]
Revenue	$ 154,518	$ 127,533
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	95,460	69,074
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	54,606	54,569
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	4,452	3,890
Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	138,374	113,809
Network Solutions [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	84,289	60,053
Network Solutions [Member] | Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	51,823	52,269
Network Solutions [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	2,262	1,487
Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue	16,144	13,724
Services & Support [Member] | Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	11,171	9,021
Services & Support [Member] | Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	2,783	2,300
Services & Support [Member] | Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 2,190	$ 2,403

Revenue - Additional Informat_2

Revenue - Additional Information (Detail1) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2022-04-01	Mar. 31, 2022
Revenue [Line Items]
Remaining performance obligations, percentage	81.10%
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	Mar. 31, 2022	Dec. 31, 2021
Revenue from Contract with Customer [Abstract]
Accounts receivable, net	$ 150,111	$ 158,742
Contract assets	8,243	464
Unearned revenue	19,454	17,737
Non-current unearned revenue	$ 9,381	$ 9,271

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Income Tax Disclosure [Line Items]
Effective tax rate expense (benefit)	(68.10%)	53.90%
Deferred tax assets, gross	$ 67,581		$ 59,643
Valuation allowance established against deferred tax assets	58,642		50,564
Deferred tax assets	8,939		9,079
Domestic [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, gross	56,460		48,265
Valuation allowance established against deferred tax assets	56,460		48,265
Increase (decrease) in deferred tax asset valuation allowance	8,200
International [Member]
Income Tax Disclosure [Line Items]
Deferred tax assets, gross	11,121		11,378
Valuation allowance established against deferred tax assets	2,182		2,299
Deferred tax assets	8,939		$ 9,079
Increase (decrease) in deferred tax asset valuation allowance	$ (100)

Income Taxes - Summary of Suppl

Income Taxes - Summary of Supplemental Balance Sheet Information Related to Deferred Tax Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	$ 67,581	$ 59,643
Valuation Allowance	(58,642)	(50,564)
Deferred Tax Assets, net	8,939	9,079
Domestic [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	56,460	48,265
Valuation Allowance	(56,460)	(48,265)
International [Member]
Operating Loss Carryforwards [Line Items]
Deferred Tax Assets	11,121	11,378
Valuation Allowance	(2,182)	(2,299)
Deferred Tax Assets, net	$ 8,939	$ 9,079

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
	Mar. 31, 2022	Mar. 31, 2021
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	$ 1,893	$ 1,807
Tax benefit for expense associated with stock options, PSUs, RSUs and restricted stock	(473)	(431)
Total stock-based compensation expense, net of tax	1,420	1,376
Stock-based Compensation Expense Included in Cost of Revenue [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	159	131
Selling, General and Administrative Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	1,124	1,098
Research and Development Expense [Member]
Share-based Compensation Arrangement by Share-based Payment Award, Compensation Cost [Line Items]
Total stock-based compensation expense	610	578
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	$ 1,734	$ 1,676

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of PSUs, RSUs and Restricted Stock Outstanding (Detail) shares in Thousands	3 Months Ended
	Mar. 31, 2022$ / sharesshares
Share-based Payment Arrangement [Abstract]
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, beginning balance | shares	1,930
Number of Shares, PSUs, RSUs and restricted stock granted | shares	328
Number of Shares, PSUs, RSUs and restricted stock vested | shares	(10)
Number of Shares, PSUs, RSUs and restricted stock forfeited | shares	(28)
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, ending balance | shares	2,220
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Beginning Balance | $ / shares	$ 14.11
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	20.21
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock vested | $ / shares	12.36
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock forfeited | $ / shares	13.72
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Ending Balance | $ / shares	$ 15.03

Stock-Based Compensation (PSUs,

Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) - USD ($) shares in Thousands, $ in Millions	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Mar. 31, 2020
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share granted	328
Options available for issuance under stockholders-approved equity plan	3,800
Performance Stock Units (PSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Share granted	300	300
Vesting period	1 year	2 years	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%	0.00%	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%	142.80%	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	$ 15.9
Recognition period of unvested compensation expense	2 years 8 months 12 days
Performance-Based PSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to other than options	$ 13.2
Recognition period of unvested compensation expense	9 months 18 days

Stock-Based Compensation - Su_2

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2022	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Number of Stock Options, Stock options outstanding, Beginning Balance	1,721
Number of Stock Options, Stock options exercised	(33)
Number of Stock Options, Stock options expired	(9)
Number of Stock Options, Stock options outstanding, Ending Balance	1,679	1,721
Number of Stock Options, Stock options exercisable	1,679
Weighted Avg. Exercise Price, Stock options outstanding, Beginning Balance	$ 19.37
Weighted Avg. Exercise Price, Stock options exercised	17.27
Weighted Avg. Exercise Price, Stock options expired	23.18
Weighted Avg. Exercise Price, Stock options outstanding, Ending Balance	19.39	$ 19.37
Weighted Avg. Exercise Price, Stock options exercisable	$ 19.39
Weighted Avg. Remaining Contractual Life In Years, Stock options outstanding	2 years 2 months 12 days	2 years 4 months 24 days
Weighted Avg. Remaining Contractual Life in Years, Stock options exercisable	2 years 2 months 12 days
Aggregate Intrinsic Value, Stock options outstanding	$ 6,669
Aggregate Intrinsic Value, Stock options exercised	101
Aggregate Intrinsic Value, Stock options expired	4
Aggregate Intrinsic Value, Stock options outstanding	1,758	$ 6,669
Aggregate Intrinsic Value, Stock options exercisable	$ 1,758

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock Options) - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Share-based Payment Arrangement [Abstract]
Unrecognized compensation expense related to stock options	$ 0
Number of Stock options, granted	0	0
Aggregate intrinsic value based on fair market value	$ 1,758,000		$ 6,669,000
Total pre-tax intrinsic value of options exercised	$ 101,000

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	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	$ 30,415	$ 30,199
Gross Unrealized Gains	2	38
Gross Unrealized Losses	(859)	(171)
Fair Value	29,558	30,066
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	9,299	10,776
Gross Unrealized Gains	1	6
Gross Unrealized Losses	(206)	(35)
Fair Value	9,094	10,747
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	1,684	1,553
Gross Unrealized Gains		2
Gross Unrealized Losses	(37)	(4)
Fair Value	1,647	1,551
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	318	322
Gross Unrealized Gains		3
Gross Unrealized Losses	(11)	(3)
Fair Value	307	322
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	4,703	4,754
Gross Unrealized Gains	1	15
Gross Unrealized Losses	(142)	(33)
Fair Value	4,562	4,736
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	14,000	12,251
Gross Unrealized Gains		12
Gross Unrealized Losses	(446)	(92)
Fair Value	13,554	12,171
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Amortized Cost	411	543
Gross Unrealized Losses	(17)	(4)
Fair Value	$ 394	$ 539

Investments - Contractual Matur

Investments - Contractual Maturities of Debt Securities and Other Investments (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities, Fair Value/Carrying Value	$ 29,558	$ 30,066
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	295
One to two years	5,965
Two to three years	2,596
Three to five years	238
Available-for-sale debt securities, Fair Value/Carrying Value	9,094	10,747
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	269
One to two years	1,265
Two to three years	113
Available-for-sale debt securities, Fair Value/Carrying Value	1,647	1,551
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Three to five years	49
More than ten years	258
Available-for-sale debt securities, Fair Value/Carrying Value	307	322
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	1,050
One to two years	479
Two to three years	289
Three to five years	371
Five to ten years	915
More than ten years	1,458
Available-for-sale debt securities, Fair Value/Carrying Value	4,562	4,736
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Less than one year	979
One to two years	4,800
Two to three years	7,106
Three to five years	669
Available-for-sale debt securities, Fair Value/Carrying Value	13,554	12,171
Foreign Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Two to three years	394
Available-for-sale debt securities, Fair Value/Carrying Value	$ 394	$ 539

Investments - Gross Realized Ga

Investments - Gross Realized Gains and Losses on Sale of Debt Securities (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Gross realized gain on debt securities	$ 12	$ 87
Gross realized loss on debt securities	(40)	(16)
Total (loss) gain recognized, net	$ (28)	$ 71

Investments - Additional Inform

Investments - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Schedule of Investments [Line Items]
Available-for-sale debt securities, allowance for credit losses	$ 0	$ 0
Purchase an available-for-sale debt securities with credit deterioration	0
Carrying value of investment	1,000,000		$ 1,000,000
Asset impairments	0	0	400,000
Cumulative asset impairment charges	2,400,000
Unsecured loan converted to equity investment			500,000
Secured Loans Receivable [Member]
Schedule of Investments [Line Items]
Asset impairments	0	$ 0	500,000
Long-term Investments [Member]
Schedule of Investments [Line Items]
Secured note receivable, noncurrent	$ 400,000		$ 400,000
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
	Mar. 31, 2022	Mar. 31, 2021
Investments, Debt and Equity Securities [Abstract]
Realized (loss) gain on equity securities sold	$ (25)	$ 24
Unrealized (loss) gain on equity securities held	(3,362)	901
Total (loss) gain recognized, net	$ (3,387)	$ 925

Investments - Cash Equivalents

Investments - Cash Equivalents and Investments held at Fair Value (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	$ 29,558	$ 30,066
Marketable equity securities	1,000	1,000
Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	67,239	70,259
Fair Value, Measurements [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	51,235	52,364
Fair Value, Measurements [Member] | Significant Other Observable Inputs (Level 2) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	16,004	17,895
Money Market Funds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	457	652
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	457	652
Corporate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	9,094	10,747
Corporate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	9,094	10,747
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	9,094	10,747
Municipal Fixed-Rate Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	1,647	1,551
Municipal Fixed-Rate Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	1,647	1,551
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	1,647	1,551
Asset-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	307	322
Asset-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	307	322
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	307	322
Mortgage/Agency-Backed Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	4,562	4,736
Mortgage/Agency-Backed Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	4,562	4,736
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	4,562	4,736
U.S. Government Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	13,554	12,171
U.S. Government Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	13,554	12,171
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]
Available-for-sale debt securities	13,554	12,171
Foreign Government Securities / Bonds [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	394	539
Foreign Government Securities / Bonds [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Available-for-sale debt securities	394	539
Foreign Government Securities / 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	394	539
Marketable Equity Securities - Various Industries [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	11,143	12,606
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	11,143	12,606
Deferred Compensation Plan Assets [Member] | Fair Value, Measurements [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	26,081	26,935
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	$ 26,081	$ 26,935

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Inventory Disclosure [Abstract]
Raw materials	$ 100,644	$ 74,709
Work in process	2,232	2,143
Finished goods	68,245	63,039
Total Inventory, net	$ 171,121	$ 139,891

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Millions	Mar. 31, 2022	Mar. 31, 2021
Inventory Disclosure [Abstract]
Inventory valuation reserves	$ 46.3	$ 44.6

Property, Plant and Equipment -

Property, Plant and Equipment - Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Land	$ 4,575	$ 4,575
Building and land improvements	35,667	35,578
Building	68,161	68,157
Furniture and fixtures	19,956	19,917
Computer hardware and software	73,440	72,274
Engineering and other equipment	134,438	134,771
Total property, plant and equipment	336,237	335,272
Less: accumulated depreciation	(281,853)	(279,506)
Total property, plant and equipment, net	$ 54,384	$ 55,766

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Property, Plant and Equipment [Abstract]
Asset impairments	$ 0	$ 0	$ 400,000
Depreciation	$ 2,800,000	$ 3,100,000

Goodwill - Additional Informati

Goodwill - Additional Information (Detail) - USD ($)	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
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	Mar. 31, 2022	Dec. 31, 2021
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 36,047	$ 36,166
Accumulated Amortization	(17,642)	(16,873)
Net Book Value	18,405	19,293
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	20,677	20,796
Accumulated Amortization	(10,192)	(9,906)
Net Book Value	10,485	10,890
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	8,200	8,200
Accumulated Amortization	(3,967)	(3,683)
Net Book Value	4,233	4,517
Licensed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	5,900	5,900
Accumulated Amortization	(2,650)	(2,486)
Net Book Value	3,250	3,414
Licensing Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	560	560
Accumulated Amortization	(243)	(225)
Net Book Value	317	335
Patent [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	500	500
Accumulated Amortization	(380)	(363)
Net Book Value	120	137
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	210	210
Accumulated Amortization	(210)	(210)
Net Book Value

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Impairment losses of intangible assets	$ 0	$ 0
Amortization expense	900,000	1,000,000
Impairment losses of long-lived assets	$ 0	$ 0

Intangible Assets - Estimated F

Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2022	$ 2,601
2023	3,316
2024	3,224
2025	3,023
2026	1,986
Thereafter	4,255
Net Book Value	$ 18,405	$ 19,293

Leases - Net Investment in Sale

Leases - Net Investment in Sales-Type Leases (Detail) - USD ($) $ in Thousands	Mar. 31, 2022	Dec. 31, 2021
Sales-Type Lease, Net Investment in Lease, before Allowance for Credit Loss [Abstract]
Current minimum lease payments receivable	$ 66	$ 92
Non-current minimum lease payments receivable	1	4
Total minimum lease payments receivable	67	96
Less: Current unearned revenue	50	70
Less: Non-current unearned revenue		1
Net investment in sales-type leases	$ 17	$ 25

Cadence Revolving Credit Agre_2

Cadence Revolving Credit Agreement - Additional Information (Detail) - USD ($)	Nov. 02, 2021	Mar. 31, 2022
Line Of Credit Facility [Line Items]
Repayment of debt under revolving credit agreement		$ 8,000,000
Cadence Bank, N.A [Member] | Secured Revolving Credit Facility [Member] | Revolving Credit and Security Agreement (The "Cadence Revolving Credit Agreement") [Member]
Line Of Credit Facility [Line Items]
Secured revolving credit facility amount	$ 10,000,000
Credit agreement maturity period	Nov. 3, 2022
Maximum loan to value ratio percentage	75.00%
Maximum interest rate in no event time	1.50%
Repayment of debt under revolving credit agreement		$ 8,000,000
Cadence Bank, N.A [Member] | Secured Revolving Credit Facility [Member] | Revolving Credit and Security Agreement (The "Cadence Revolving Credit Agreement") [Member] | Screen Rate [Member]
Line Of Credit Facility [Line Items]
Debt instrument interest over screen rate	1.50%

Stockholders' Equity - Addition

Stockholders' Equity - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2022shares
Equity [Abstract]
Stock repurchased, shares	0
Additional shares authorized for purchase	2,500,000
Maximum shares authorized for repurchase, prior and new announcements and total after new announcement	5,000,000

Stockholders' Equity - Changes

Stockholders' Equity - Changes in Accumulated Other Comprehensive Loss, Net of Tax by Component (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 357,102	$ 372,944
Other comprehensive income (loss) before reclassifications	(1,880)	(1,920)
Amounts reclassified from accumulated other comprehensive income (loss)	238	(36)
Ending Balance	352,316	370,375
ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	385	385
Ending Balance	385	385
Accumulated Other Comprehensive Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(11,914)	(11,639)
Ending Balance	(13,556)	(13,595)
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(552)	32
Other comprehensive income (loss) before reclassifications	(975)	(57)
Amounts reclassified from accumulated other comprehensive income (loss)	251	(135)
Ending Balance	(1,276)	(160)
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(5,613)	(9,621)
Amounts reclassified from accumulated other comprehensive income (loss)	(13)	99
Ending Balance	(5,626)	(9,522)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(6,134)	(2,435)
Other comprehensive income (loss) before reclassifications	(905)	(1,863)
Ending Balance	$ (7,039)	$ (4,298)

Stockholders' Equity - Reclassi

Stockholders' Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
(Loss) Income Before Income Taxes	$ (3,535)	$ 1,944
Tax benefit (expense)	2,408	(1,048)
Net (Loss) Income	(1,127)	896
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
(Loss) Income Before Income Taxes	(311)	35
Tax benefit (expense)	73	1
Net (Loss) Income	(238)	36
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] | Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gain (loss)	(330)	178
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] | Other Income (Expense), Net [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit plan adjustments - actuarial gain	$ 19	$ (143)

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
	Mar. 31, 2022	Mar. 31, 2021
Equity [Abstract]
Unrealized gain (loss) on available-for-sale securities, Before-Tax Amount	$ (1,283)	$ (75)
Unrealized gain (loss) on available-for-sale securities, Tax (Expense) Benefit	308	18
Unrealized gain (loss) on available-for-sale securities, Net-of-Tax Amount	(975)	(57)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Before-Tax Amount	330	(178)
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Tax (Expense) Benefit	(79)	43
Reclassification adjustment for amounts related to available-for-sale investments included in net income (loss), Net-of-Tax Amount	251	(135)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Before-Tax Amount	(19)	143
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Tax (Expense) Benefit	6	(44)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net income (loss), Net-of-Tax Amount	(13)	99
Foreign currency translation adjustment, Before-Tax Amount	(905)	(1,863)
Foreign currency translation adjustment, Net-of-Tax Amount	(905)	(1,863)
Total Other Comprehensive Income (Loss), Before-Tax Amount	(1,877)	(1,973)
Total Other Comprehensive Income (Loss), Tax (Expense) Benefit	235	17
Other Comprehensive (Loss) Income, net of tax	$ (1,642)	$ (1,956)

(Loss) Earnings Per Share - Sum

(Loss) Earnings 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
	Mar. 31, 2022	Mar. 31, 2021
Numerator
Net (loss) income	$ (1,127)	$ 896
Denominator
Weighted average number of shares – basic	49,113	48,336
Effect of dilutive securities
Stock options		56
PSUs, RSUs and restricted stock		612
Weighted average number of shares – diluted	49,113	49,004
(Loss) earnings per share - basic	$ (0.02)	$ 0.02
(Loss) earnings per share - diluted	$ (0.02)	$ 0.02

(Loss) Earnings Per Share - Add

(Loss) Earnings Per Share - Additional Information (Detail) - shares shares in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted earnings per share	100	700
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	5	1

Segment Information - Additiona

Segment Information - Additional Information (Detail)	3 Months Ended
	Mar. 31, 2022CategorySegment
Segment Reporting [Abstract]
Number of reportable segments | Segment	2
Number of categories | Category	3

Segment Information - Revenue a

Segment Information - Revenue and Gross Profit of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Segment Reporting Information [Line Items]
Revenue	$ 154,518	$ 127,533
Gross Profit	54,316	53,601
Network Solutions [Member]
Segment Reporting Information [Line Items]
Revenue	138,374	113,809
Gross Profit	47,721	48,808
Services & Support [Member]
Segment Reporting Information [Line Items]
Revenue	16,144	13,724
Gross Profit	$ 6,595	$ 4,793

Segment Information - Revenue I

Segment Information - Revenue Information by Category (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Disaggregation Of Revenue [Line Items]
Revenue	$ 154,518	$ 127,533
Access & Aggregation [Member]
Disaggregation Of Revenue [Line Items]
Revenue	95,460	69,074
Subscriber Solutions & Experience [Member]
Disaggregation Of Revenue [Line Items]
Revenue	54,606	54,569
Traditional & Other Products [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 4,452	$ 3,890

Segment Information - Revenue_2

Segment Information - Revenue Information by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Revenue from External Customer [Line Items]
Revenue	$ 154,518	$ 127,533
United States [Member]
Revenue from External Customer [Line Items]
Revenue	99,048	86,485
United Kingdom [Member]
Revenue from External Customer [Line Items]
Revenue	30,388	8,042
Germany [Member]
Revenue from External Customer [Line Items]
Revenue	10,920	14,374
Other International [Member]
Revenue from External Customer [Line Items]
Revenue	$ 14,162	$ 18,632

Liability for Warranty Return_2

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Dec. 31, 2021	Mar. 31, 2021	Dec. 31, 2020
Product Warranties Disclosures [Abstract]
Period of assurance-based warranty for product defects	90 days to five years
Liability for warranty obligations	$ 5,143	$ 5,403	$ 6,472	$ 7,146

Liability for Warranty Return_3

Liability for Warranty Returns - Summary of Warranty Expense and Write-off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 5,403	$ 7,146
Plus: Amounts charged to cost and expenses	344	(231)
Less: Deductions	(604)	(443)
Balance at end of period	$ 5,143	$ 6,472

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) $ in Millions	Aug. 30, 2021shares	Mar. 31, 2020Officer	Mar. 31, 2022USD ($)	Feb. 14, 2022	Jan. 26, 2022	Dec. 31, 2021USD ($)	Mar. 31, 2021USD ($)
Contingencies And Commitments [Line Items]
Commitments related to performance bonds			$ 20.9			$ 22.9
Commitments related to performance bonds expiration month and year			2025-04
Letter of credit secured by pledge of a portion of fixed income securities			$ 18
Commitments towards private equity funds			4.9
Investment Commitments [Member]
Contingencies And Commitments [Line Items]
Aggregate investment committed in private equity funds			5
Long-term Investments [Member]
Contingencies And Commitments [Line Items]
Letter of credit secured by pledge of a portion of fixed income securities			17.9
Minimum [Member]
Contingencies And Commitments [Line Items]
Collateral value required to be maintained							$ 15
Maximum [Member] | Restricted Cash [Member]
Contingencies And Commitments [Line Items]
Letter of credit secured by pledge of a portion of fixed income securities			$ 0.1
Acorn HoldCo, Inc., [Member]
Contingencies And Commitments [Line Items]
Business combination date of agreement	Aug. 30, 2021
Percentage of ownership interest acquired				66.00%
Acorn HoldCo, Inc., [Member] | Minimum [Member]
Contingencies And Commitments [Line Items]
Percentage of ownership interest acquired					60.00%
Acorn HoldCo, Inc., [Member] | ADTRAN INC [Member]
Contingencies And Commitments [Line Items]
Percentage of ownership interest acquired	54.00%
Acorn HoldCo, Inc., [Member] | ADTRAN INC [Member] | Common Stock [Member]
Contingencies And Commitments [Line Items]
Number of shares issuable for each share of acquired entity | shares	1
Acorn HoldCo, Inc., [Member] | ADVA Optical Networking SE, [Member]
Contingencies And Commitments [Line Items]
Percentage of ownership interest acquired	46.00%
Acorn HoldCo, Inc., [Member] | ADVA Optical Networking SE, [Member] | Common Stock [Member]
Contingencies And Commitments [Line Items]
Number of shares issuable for each share of acquired entity | shares	0.8244
Current Executive Officers [Member]
Contingencies And Commitments [Line Items]
Number of officers | Officer		2
Former Executive Officers [Member]
Contingencies And Commitments [Line Items]
Number of officers | Officer		1

Restructuring - Additional Info

Restructuring - Additional Information (Detail) $ in Millions	3 Months Ended
	Mar. 31, 2022USD ($)
Restructuring and Related Activities [Abstract]
Cumulative amount of restructuring expenses incurred for restructuring plan	$ 12.7

Restructuring - Schedule of Rec

Restructuring - Schedule of Reconciliation of Restructuring Liability (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Restructuring and Related Activities [Abstract]
Balance at beginning of period	$ 1,514	$ 4,186	$ 4,186
Plus: Amounts charged to cost and expense	2	$ 301	411
Less: Amounts paid	(1,256)		(3,083)
Balance at end of period	$ 260		$ 1,514

Restructuring - Schedule of Com

Restructuring - Schedule of Components of Restructuring Expenses Including in Condensed Consolidated Statements of (Loss) Income (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 2	$ 301	$ 411
Cost of Revenue [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	0	15
Selling, General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	2	142
Research and Development Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	0	144
Network Solutions [Member] | Cost of Revenue [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	0	12
Services & Support [Member] | Cost of Revenue [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 0	$ 3

Restructuring - Schedule of C_2

Restructuring - Schedule of Components of Restructuring Expense by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2022	Mar. 31, 2021	Dec. 31, 2021
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 2	$ 301	$ 411
United States [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	2	209
International [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 0	$ 92

Subsequent Events - Additional

Subsequent Events - Additional Information (Detail) - USD ($)	May 04, 2022	Apr. 01, 2022	Jun. 02, 2022
Subsequent Event [Member]
Subsequent Event [Line Items]
Dividend declaration date	May 4, 2022
Common stock dividends per share declared	$ 0.09
Dividend record date	May 19, 2022
Dividend payment date	Jun. 2, 2022
Subsequent Event [Member] | Credit Agreement and Revolving Line of Credit Note (The "Wells Revolving Credit Agreement") [Member] | Wells Fargo Bank [Member] | Secured Revolving Credit Facility [Member]
Subsequent Event [Line Items]
New secured revolving credit facility amount		$ 25,000,000
Credit agreement maturity period		Apr. 1, 2023
Subsequent Event [Member] | Credit Agreement and Revolving Line of Credit Note (The "Wells Revolving Credit Agreement") [Member] | Wells Fargo Bank [Member] | Secured Revolving Credit Facility [Member] | Daily Simple SOFR [Member]
Subsequent Event [Line Items]
Credit facility, floor rate		0.00%
Scenario Forecast [Member]
Subsequent Event [Line Items]
Quarterly dividend payable, aggregate amount			$ 4,400,000
Senior Funded Debt to EBITDA Ratio One [Member] | Subsequent Event [Member] | Credit Agreement and Revolving Line of Credit Note (The "Wells Revolving Credit Agreement") [Member] | Wells Fargo Bank [Member] | Secured Revolving Credit Facility [Member] | Daily Simple SOFR [Member]
Subsequent Event [Line Items]
Applicable margin rate		1.00%
Senior Funded Debt to EBITDA Ratio Two [Member] | Subsequent Event [Member] | Credit Agreement and Revolving Line of Credit Note (The "Wells Revolving Credit Agreement") [Member] | Wells Fargo Bank [Member] | Secured Revolving Credit Facility [Member] | Daily Simple SOFR [Member]
Subsequent Event [Line Items]
Applicable margin rate		1.25%
Senior Funded Debt to EBITDA Ratio Three [Member] | Subsequent Event [Member] | Credit Agreement and Revolving Line of Credit Note (The "Wells Revolving Credit Agreement") [Member] | Wells Fargo Bank [Member] | Secured Revolving Credit Facility [Member] | Daily Simple SOFR [Member]
Subsequent Event [Line Items]
Applicable margin rate		1.50%
Senior Funded Debt to EBITDA Ratio Four [Member] | Subsequent Event [Member] | Credit Agreement and Revolving Line of Credit Note (The "Wells Revolving Credit Agreement") [Member] | Wells Fargo Bank [Member] | Secured Revolving Credit Facility [Member] | Daily Simple SOFR [Member]
Subsequent Event [Line Items]
Applicable margin rate		2.00%