ADTRAN (ADTN) 10-Q 12 Nov 24 2024 Q3 Quarterly report Financial data

Document and Entity Information

Document and Entity Information - shares	9 Months Ended
	Sep. 30, 2024	Nov. 01, 2024
Cover [Abstract]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2024
Document Fiscal Year Focus	2024
Document Fiscal Period Focus	Q3
Entity Registrant Name	ADTRAN Holdings, 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		79,248,942
Entity Current Reporting Status	Yes
Entity Interactive Data Current	Yes
Entity Shell Company	false
Entity File Number	001-41446
Entity Tax Identification Number	87-2164282
Entity Address, Address Line One	901 Explorer Boulevard
Entity Address, City or Town	Huntsville
Entity Address, State or Province	AL
Entity Address, Postal Zip Code	35806-2807
City Area Code	256
Local Phone Number	963-8000
Entity Incorporation, State or Country Code	DE
Document Quarterly Report	true
Document Transition Report	false
Title of 12(b) Security	Common Stock, Par Value $0.01 per share
Security Exchange Name	NASDAQ

Condensed Consolidated Balance

Condensed Consolidated Balance Sheets (Unaudited) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Current Assets
Cash and cash equivalents	$ 88,456	$ 87,167
Accounts receivable, less allowance for credit losses of $420 and $400 as of September 30, 2024 and December 31, 2023, respectively	172,025	216,445
Other receivables	12,871	17,450
Income tax receivable	13,466	7,933
Inventory, net	282,926	362,295
Prepaid expenses and other current assets	69,112	45,566
Total Current Assets	638,856	736,856
Property, plant and equipment, net	147,428	123,020
Deferred tax assets	25,697	25,787
Goodwill	56,884	353,415
Intangibles, net	286,098	327,985
Other non-current assets	86,677	87,706
Long-term investments	31,506	27,743
Total Assets	1,273,146	1,682,512
Current Liabilities
Accounts payable	173,354	162,922
Unearned revenue	54,615	46,731
Accrued expenses and other liabilities	34,482	36,204
Accrued wages and benefits	40,366	27,030
Income tax payable, net	2,007	5,221
Total Current Liabilities	304,824	278,108
Non-current revolving credit agreement outstanding	189,849	195,000
Deferred tax liabilities	21,483	35,655
Non-current unearned revenue	24,901	25,109
Non-current pension liability	12,149	12,543
Deferred compensation liability	32,046	29,039
Non-current lease obligations	25,635	31,420
Other non-current liabilities	26,489	28,657
Total Liabilities	637,376	635,531
Commitments and contingencies (see Note 18)
Redeemable Non-Controlling Interest	421,776	442,152
Equity
Common stock, par value $0.01 per share; 200,000 shares authorized; 79,233 shares issued and 78,967 outstanding as of September 30, 2024 and 78,970 shares issued and 78,674 outstanding as of December 31, 2023	792	790
Additional paid-in capital	806,187	795,304
Accumulated other comprehensive income	47,377	47,465
Retained deficit	(635,164)	(232,905)
Treasury stock at cost: 266 and 297 shares as of September 30, 2024 and December 31, 2023, respectively	(5,198)	(5,825)
Total Equity	213,994	604,829
Total Liabilities, Redeemable Non-Controlling Interest and Equity	$ 1,273,146	$ 1,682,512

Condensed Consolidated Balanc_2

Condensed Consolidated Balance Sheets (Unaudited) (Parenthetical) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Statement of Financial Position [Abstract]
Accounts receivable, allowance for credit losses	$ 420	$ 400
Common stock, par value	$ 0.01	$ 0.01
Common stock, shares authorized	200,000,000	200,000,000
Common stock, shares issued	79,233,000	78,970,000
Common stock, shares outstanding	78,967,000	78,674,000
Treasury stock, shares	266,000	297,000

Condensed Consolidated Statemen

Condensed Consolidated Statements of Loss (Unaudited) - USD ($) shares in Thousands		3 Months Ended			9 Months Ended
		Sep. 30, 2024		Sep. 30, 2023	Sep. 30, 2024		Sep. 30, 2023
Revenue
Total Revenue		$ 227,704,000		$ 272,331,000	$ 679,868,000		$ 923,621,000
Cost of Revenue
Total Cost of Revenue		142,453,000		198,094,000	440,787,000		669,023,000
Gross Profit		85,251,000		74,237,000	239,081,000		254,598,000
Selling, general and administrative expenses		57,620,000		62,907,000	176,214,000		196,887,000
Research and development expenses		51,615,000		62,752,000	172,253,000		203,493,000
Goodwill impairment		0		37,874,000	292,583,000		37,874,000
Operating Loss		(23,984,000)		(89,296,000)	(401,969,000)		(183,656,000)
Interest and dividend income		664,000		521,000	1,427,000		1,183,000
Interest expense		(5,679,000)		(4,507,000)	(17,183,000)		(11,858,000)
Net investment gain (loss)		1,382,000		(1,443,000)	4,507,000		1,071,000
Other (expense) income, net		(850,000)		2,523,000	(441,000)		4,714,000
Loss Before Income Taxes		(28,467,000)		(92,202,000)	(413,659,000)		(188,546,000)
Income tax (expense) benefit		(390,000)		16,553,000	16,121,000		36,229,000
Net Loss		(28,857,000)		(75,649,000)	(397,538,000)		(152,317,000)
Less: Net Income attributable to non-controlling interest	[1]	2,382,000		2,561,000	7,417,000		4,380,000
Net Loss attributable to ADTRAN Holdings, Inc.		$ (31,239,000)		$ (78,210,000)	$ (404,955,000)		$ (156,697,000)
Weighted average shares outstanding – basic		78,952		78,389	78,873		78,378
Weighted average shares outstanding – diluted		78,952		78,389	78,873		78,378
Loss per common share attributable to ADTRAN Holdings, Inc. - basic		$ (0.36)	[2]	$ (1)	$ (5.1)	[2]	$ (2)
Loss per common share attributable to ADTRAN Holdings, Inc. - diluted		$ (0.36)	[2]	$ (1)	$ (5.1)	[2]	$ (2)
Network Solutions [Member]
Revenue
Total Revenue		$ 181,488,000		$ 228,564,000	$ 541,955,000		$ 793,984,000
Cost of Revenue
Total Cost of Revenue		126,103,000		160,244,000	376,886,000		596,334,000
Gross Profit		55,713,000		47,277,000	156,472,000		176,607,000
Network Solutions Other (Credits), Charges and Inventory Write-Down [Member]
Cost of Revenue
Total Cost of Revenue		(328,000)		21,043,000	8,597,000		21,043,000
Services & Support [Member]
Revenue
Total Revenue		46,216,000		43,767,000	137,913,000		129,637,000
Cost of Revenue
Total Cost of Revenue		16,678,000		16,807,000	55,304,000		51,646,000
Gross Profit		$ 29,538,000		26,960,000	$ 82,609,000		$ 77,991,000
Goodwill impairment				$ 37,900,000
[1] For the three and nine months ended September 30, 2024, we accrued $ 2.4 million and $ 7.4 million, respectively, net income attributable to non-controlling interest, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA. For the three and nine months ended September 30, 2023, we accrued $ 2.6 million and $ 7.6 million, respectively, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA, partially offset by a $ 3.2 million net loss attributable to non-controlling interests pre-DPLTA for the nine months ended September 30, 2023. Loss per common share attributable to ADTRAN Holdings, Inc. - basic and diluted - reflects a $ 3.0 million effect of redemption of RNCI for the three and nine months ended September 30, 2024. See Note 15 for additional information.

Condensed Consolidated Statem_2

Condensed Consolidated Statements of Loss (Unaudited) (Parenthetical) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Net gain (loss) attributable to redeemable non-controlling interest	[1]	$ 2,382	$ 2,561	$ 7,417	$ 4,380
Gain on redemption of redeemable non-controlling interest		2,976		2,976
Pre-DPLTA [Member]
Net gain (loss) attributable to redeemable non-controlling interest					3,200
Post-DPLTA [Member]
Recurring cash compensation earned		$ 2,400	$ 2,600	$ 7,400	$ 7,600
[1] For the three and nine months ended September 30, 2024, we accrued $ 2.4 million and $ 7.4 million, respectively, net income attributable to non-controlling interest, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA. For the three and nine months ended September 30, 2023, we accrued $ 2.6 million and $ 7.6 million, respectively, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA, partially offset by a $ 3.2 million net loss attributable to non-controlling interests pre-DPLTA for the nine months ended September 30, 2023.

Condensed Consolidated Statem_3

Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Statement of Comprehensive Income [Abstract]
Net loss	$ (28,857)	$ (75,649)	$ (397,538)	$ (152,317)
Other Comprehensive Income (Loss), net of tax
Net unrealized gain on available-for-sale securities	0	391	0	454
Defined benefit plan adjustments	109	(83)	42	(25)
Foreign currency translation gain (loss)	18,988	(29,715)	(130)	(14,095)
Other Comprehensive Income (Loss), net of tax	19,097	(29,407)	(88)	(13,666)
Comprehensive Loss, net of tax	(9,760)	(105,056)	(397,626)	(165,983)
Less: Comprehensive Income attributable to non-controlling interest, net of tax	2,382	2,561	7,417	4,762
Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax	$ (12,142)	$ (107,617)	$ (405,043)	$ (170,745)

Condensed Consolidated Statem_4

Condensed Consolidated Statements of Changes in Equity (Unaudited) - USD ($) shares in Thousands, $ in Thousands	Total	Adtran Networks SE [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Adtran Networks SE [Member]	Retained Deficit Earnings [Member]	Treasury Stock [Member]	Accumulated Other Comprehensive Income [Member]	Non-controlling Interest [Member]
Beginning Balance at Dec. 31, 2022	$ 1,303,613		$ 781	$ 895,834		$ 55,338	$ (4,125)	$ 26,126	$ 329,659
Beginning Balance, Shares at Dec. 31, 2022			78,088
Net (loss) income	(40,453)					(37,274)			(3,179)
Annual recurring compensation earned	(2,464)					(2,464)
Reclassification and remeasurement from equity to mezzanine equity for non-controlling interests in Adtran Networks	(443,757)			(116,895)					(326,862)
Other comprehensive income (loss), net of tax	8,783							8,401	382
Dividend payments to ADTRAN Holdings, Inc. shareholders ($0.09 per share)	(7,076)					(7,076)
Deferred compensation adjustments, net of tax	(1,792)						(1,792)
ADTRAN RSUs and restricted stock vested	(138)		$ 6			(144)
ADTRAN RSUs and restricted stock vested, Shares			561
ADTRAN Stock options exercised	58					58
ADTRAN Stock options exercised, Shares			6
ADTRAN Stock-based compensation expense	3,812	$ 9		3,812	$ 9
Redemption of redeemable non-controlling interest	343					343
Ending Balance at Mar. 31, 2023	820,938		$ 787	782,760		8,781	(5,917)	34,527
Ending Balance, Shares at Mar. 31, 2023			78,655
Beginning Balance at Dec. 31, 2022	1,303,613		$ 781	895,834		55,338	(4,125)	26,126	329,659
Beginning Balance, Shares at Dec. 31, 2022			78,088
Other comprehensive income (loss), net of tax	15,741
Ending Balance at Jun. 30, 2023	786,409		$ 787	787,153		(37,073)	(5,943)	41,485
Ending Balance, Shares at Jun. 30, 2023			78,661
Beginning Balance at Dec. 31, 2022	1,303,613		$ 781	895,834		55,338	(4,125)	26,126	329,659
Beginning Balance, Shares at Dec. 31, 2022			78,088
Other comprehensive income (loss), net of tax	(13,666)
Ending Balance at Sep. 30, 2023	675,651		$ 787	791,290		(122,534)	(5,970)	12,078
Ending Balance, Shares at Sep. 30, 2023			78,688
Beginning Balance at Dec. 31, 2022	1,303,613		$ 781	895,834		55,338	(4,125)	26,126	$ 329,659
Beginning Balance, Shares at Dec. 31, 2022			78,088
Other comprehensive income (loss), net of tax	21,721							21,339
Ending Balance at Dec. 31, 2023	$ 604,829		$ 790	795,304		(232,905)	(5,825)	47,465
Ending Balance, Shares at Dec. 31, 2023	78,970		78,970
Beginning Balance at Mar. 31, 2023	$ 820,938		$ 787	782,760		8,781	(5,917)	34,527
Beginning Balance, Shares at Mar. 31, 2023			78,655
Net (loss) income	(36,215)					(36,215)
Annual recurring compensation earned	(2,534)					(2,534)
Other comprehensive income (loss), net of tax	6,958							6,958
Dividend payments to ADTRAN Holdings, Inc. shareholders ($0.09 per share)	(7,076)					(7,076)
Dividends accrued for RSUs	9					9
Deferred compensation adjustments, net of tax	(26)						(26)
ADTRAN RSUs and restricted stock vested	(44)					(44)
ADTRAN RSUs and restricted stock vested, Shares			6
ADTRAN Stock options exercised		92			92
ADTRAN Stock-based compensation expense	4,291	10		4,291	10
Redemption of redeemable non-controlling interest	6					6
Ending Balance at Jun. 30, 2023	786,409		$ 787	787,153		(37,073)	(5,943)	41,485
Ending Balance, Shares at Jun. 30, 2023			78,661
Net (loss) income	(75,649)					(75,649)
Annual recurring compensation earned	(2,561)					(2,561)
Other comprehensive income (loss), net of tax	(29,407)							(29,407)
Dividend payments to ADTRAN Holdings, Inc. shareholders ($0.09 per share)	(7,085)					(7,085)
Dividends accrued for RSUs	(8)					(8)
Deferred compensation adjustments, net of tax	(27)						(27)
ADTRAN RSUs and restricted stock vested	(175)					(175)
ADTRAN RSUs and restricted stock vested, Shares			25
ADTRAN Stock options exercised	15				8	15
ADTRAN Stock options exercised, Shares			2
ADTRAN Stock-based compensation expense	4,126			4,126	3
Redemption of redeemable non-controlling interest	2					2
Ending Balance at Sep. 30, 2023	675,651		$ 787	791,290		(122,534)	(5,970)	12,078
Ending Balance, Shares at Sep. 30, 2023			78,688
Beginning Balance at Dec. 31, 2023	$ 604,829		$ 790	795,304		(232,905)	(5,825)	47,465
Beginning Balance, Shares at Dec. 31, 2023	78,970		78,970
Net (loss) income	$ (321,670)					(321,670)
Annual recurring compensation earned	(2,531)					(2,531)
Other comprehensive income (loss), net of tax	(17,804)							(17,804)
Deferred compensation adjustments, net of tax	262			(368)		3	627
ADTRAN RSUs and restricted stock vested	(242)		$ 1			(243)
ADTRAN RSUs and restricted stock vested, Shares			110
ADTRAN Stock options exercised	219					219
ADTRAN Stock options exercised, Shares			36
ADTRAN Stock-based compensation expense	3,957	4		3,957	4
Redemption of redeemable non-controlling interest	1					1
Ending Balance at Mar. 31, 2024	267,025		$ 791	798,897		(557,126)	(5,198)	29,661
Ending Balance, Shares at Mar. 31, 2024			79,116
Beginning Balance at Dec. 31, 2023	$ 604,829		$ 790	795,304		(232,905)	(5,825)	47,465
Beginning Balance, Shares at Dec. 31, 2023	78,970		78,970
Other comprehensive income (loss), net of tax	$ (19,185)
Ending Balance at Jun. 30, 2024	219,954		$ 791	802,737		(606,656)	(5,198)	28,280
Ending Balance, Shares at Jun. 30, 2024			79,121
Beginning Balance at Dec. 31, 2023	$ 604,829		$ 790	795,304		(232,905)	(5,825)	47,465
Beginning Balance, Shares at Dec. 31, 2023	78,970		78,970
Other comprehensive income (loss), net of tax	$ (88)
ADTRAN Stock options exercised, Shares	36
Ending Balance at Sep. 30, 2024	$ 213,994		$ 792	806,187		(635,164)	(5,198)	47,377
Ending Balance, Shares at Sep. 30, 2024	79,233		79,233
Beginning Balance at Mar. 31, 2024	$ 267,025		$ 791	798,897		(557,126)	(5,198)	29,661
Beginning Balance, Shares at Mar. 31, 2024			79,116
Net (loss) income	(47,011)					(47,011)
Annual recurring compensation earned	(2,504)					(2,504)
Other comprehensive income (loss), net of tax	(1,381)							(1,381)
Deferred compensation adjustments, net of tax	(3)					(3)
ADTRAN RSUs and restricted stock vested	(16)					(16)
ADTRAN RSUs and restricted stock vested, Shares			5
ADTRAN Stock-based compensation expense	3,836	4		3,836	4
Redemption of redeemable non-controlling interest	4					4
Ending Balance at Jun. 30, 2024	219,954		$ 791	802,737		(606,656)	(5,198)	28,280
Ending Balance, Shares at Jun. 30, 2024			79,121
Net (loss) income	(28,857)					(28,857)
Annual recurring compensation earned	(2,382)					(2,382)
Other comprehensive income (loss), net of tax	19,097							19,097
ADTRAN RSUs and restricted stock vested	(244)		$ 1			(245)
ADTRAN RSUs and restricted stock vested, Shares			112
ADTRAN Stock-based compensation expense	3,623	$ 17		3,623	$ 17
Redemption of redeemable non-controlling interest	2,976					2,976
Modification of Stock Options	(190)			(190)
Ending Balance at Sep. 30, 2024	$ 213,994		$ 792	$ 806,187		$ (635,164)	$ (5,198)	$ 47,377
Ending Balance, Shares at Sep. 30, 2024	79,233		79,233

Condensed Consolidated Statem_5

Condensed Consolidated Statements of Changes in Equity (Unaudited) (Parenthetical) - $ / shares	3 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023
Statement of Stockholders' Equity [Abstract]
Dividend payments	$ 0.09	$ 0.09	$ 0.09

Condensed Consolidated Statem_6

Condensed Consolidated Statements of Cash Flows (Unaudited) - USD ($)	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023
Cash flows from operating activities:
Net loss	$ (397,538,000)	$ (152,317,000)
Adjustments to reconcile net loss to net cash provided by (used in) operating activities:
Depreciation and amortization	68,421,000	91,422,000
Goodwill Impairment	292,583,000	37,874,000
Amortization of debt issuance cost	1,013,000	607,000
Gain on investments, net	(4,238,000)	(3,316,000)
Net loss on disposal of property, plant and equipment	203,000
Stock-based compensation expense	11,417,000	12,229,000
Deferred income taxes	(13,399,000)	(45,941,000)
Other, net	(267,000)	204,000
Inventory write down - business efficiency program	4,135,000	21,043,000
Inventory reserves	6,667,000	29,836,000
Changes in operating assets and liabilities:
Accounts receivable, net	59,446,000	47,347,000
Other receivables	4,875,000	8,340,000
Income taxes receivable, net	(5,682,000)
Inventory	69,412,000	536,000
Prepaid expenses, other current assets and other assets	(20,083,000)	1,816,000
Accounts payable	9,697,000	(87,903,000)
Accrued expenses and other liabilities	15,039,000	6,476,000
Income taxes payable, net	(3,175,000)	2,433,000
Net cash provided by (used in) operating activities	98,526,000	(29,314,000)
Cash flows from investing activities:
Purchases of property, plant and equipment	(48,183,000)	(33,674,000)
Proceeds from sales and maturities of available-for-sale investments	1,195,000	10,545,000
Purchases of available-for-sale investments	(195,000)	(807,000)
Proceeds from beneficial interests in securitized accounts receivable	282,000	1,178,000
Net cash used in investing activities	(46,901,000)	(22,758,000)
Cash flows from financing activities:
Tax withholdings related to stock-based compensation settlements	(189,000)	(6,331,000)
Proceeds from stock option exercises	219,000	187,000
Dividend payments		(21,237,000)
Proceeds from receivables purchase agreement	68,556,000
Repayments on receivables purchase agreement	(83,772,000)
Proceeds from draw on revolving credit agreements		163,760,000
Repayment of revolving credit agreements	(5,000,000)	(49,233,000)
Payment for redemption of redeemable non-controlling interest	(17,395,000)	(1,196,000)
Payment for annual recurring compensation to non-controlling interest	(10,084,000)
Payment of debt issuance cost	(1,994,000)	(708,000)
Repayment of notes payable		(24,931,000)
Net cash (used in) provided by financing activities	(49,659,000)	60,311,000
Net increase in cash and cash equivalents	1,966,000	8,239,000
Effect of exchange rate changes	(677,000)	(791,000)
Cash and cash equivalents, beginning of period	87,167,000	108,644,000
Cash and cash equivalents, end of period	88,456,000	116,092,000
Supplemental disclosure of cash financing activities:
Cash paid for interest	18,225,000	8,540,000
Cash paid for income taxes	9,122,000
Cash used in operating activities related to operating leases	7,380,000	7,378,000
Supplemental disclosure of non-cash investing activities:
Right-of-use assets obtained in exchange for lease obligations	2,122,000	8,490,000
Purchases of property, plant and equipment included in accounts payable	$ 952,000	$ 2,508,000

Pay vs Performance Disclosure

Pay vs Performance Disclosure - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Pay vs Performance Disclosure
Net Income (Loss)	$ (31,239)	$ (49,515)	$ (324,201)	$ (78,210)	$ (38,749)	$ (39,738)	$ (373,716)	$ (78,487)	$ (404,955)	$ (156,697)	$ (266,289)

Insider Trading Arrangements

Insider Trading Arrangements	3 Months Ended
	Sep. 30, 2024
Trading Arrangements, by Individual
Rule 10b5-1 Arrangement Adopted	false
Non-Rule 10b5-1 Arrangement Adopted	false
Rule 10b5-1 Arrangement Terminated	false
Non-Rule 10b5-1 Arrangement Terminated	false

Summary of Significant Accounti

Summary of Significant Accounting Policies	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Summary of Significant Accounting Policies	GENERAL ADTRAN Holdings, Inc. (“ADTRAN” or the “Company”) is a leading global provider of networking and communications platforms, software, systems and services focused on the broadband access market, serving a diverse domestic and international customer base in multiple countries that includes large, medium and small Service Providers, alternative Service Providers, such as utilities, municipalities and fiber overbuilders, cable/MSOs, SMBs and distributed enterprises, including Fortune 500 companies with sophisticated business continuity applications; and federal, state and local government agencies. Our innovative solutions and services enable voice, data, video and internet-communications across a variety of network infrastructures and are currently in use by millions worldwide. We support our customers through our direct global sales organization and our distribution networks. Our success depends upon our ability to increase unit volume and market share through the introduction of new products and succeeding generations of products having optimal selling prices and increased functionality as compared to both the prior generation of a product and to the products of competitors in order to gain market share. To service our customers and grow revenue, we are continually conducting research and developing new products addressing customer needs and testing those products for the specific requirements of the particular customers. We offer a broad portfolio of flexible software and hardware network solutions and services that enable Service Providers to meet today’s service demands, while enabling them to transition to the fully converged, scalable, highly-automated, cloud-controlled voice, data, internet and video network of the future. In addition to our global headquarters in Huntsville, Alabama, and our European headquarters in Munich, Germany, we have sales and research and development facilities in strategic global locations. The Company solely owns ADTRAN, Inc. and is the majority shareholder of Adtran Networks SE (“Adtran Networks”). ADTRAN, Inc. is a leading global provider of open, disaggregated networking and communications solutions. Adtran Networks is a global provider of network solutions for data, storage, voice and video services. We believe that the combined technology portfolio can best address current and future customer needs for high-speed connectivity from the network core to the end consumer, especially upon the convergence of solutions at the network edge. Liquidity, Domination and Profit and Loss Transfer Agreement and Credit Facility The DPLTA between the Company, as the controlling company, and Adtran Networks, as the controlled company, which was executed on December 1, 2022, became effective on January 16, 2023, as a result of its registration with the commercial register ( Handelsregister ) of the local court ( Amtsgericht ) at the registered seat of Adtran Networks (Jena). Under the DPLTA, subject to certain limitations pursuant to applicable law and the specific terms of the DPLTA, (i) the Company is entitled to issue binding instructions to the management board of Adtran Networks, (ii) Adtran Networks will transfer its annual profit to the Company, subject to, among other things, the creation or dissolution of certain reserves, and (iii) the Company will generally absorb the annual net loss incurred by Adtran Networks. The obligation of the Company to absorb Adtran Networks’ annual net loss applied for the first time to the loss generated by Adtran Networks in 2023. Pursuant to the terms of the DPLTA, each Adtran Networks shareholder (other than the Company) has received an offer to elect either (1) to remain an Adtran Networks shareholder and receive from us an Annual Recurring Compensation payment, or (2) to receive Exit Compensation plus guaranteed interest. The guaranteed interest under the Exit Compensation is calculated from the effective date of the DPLTA to the date the shares are tendered, less any Annual Recurring Compensation paid. The guaranteed interest rate is 5.0 % plus a variable component (according to the German Civil Code) that was 3.37 % as of September 30, 2024. Assuming all the minority holders of currently outstanding Adtran Networks shares were to elect the second option, we would be obligated to make aggregate Exit Compensation payments, including guaranteed interest, of approximately € 326.9 million or approximately $ 364.1 million, based on an exchange rate as of September 30, 2024, and reflecting interest accrued through September 30, 2024 during the pendency of the appraisal proceedings discussed below. Shareholders electing the first option of Annual Recurring Compensation may later elect the second option. The opportunity for outside Adtran Networks shareholders to tender Adtran Networks shares in exchange for Exit Compensation had been scheduled to expire on March 16, 2023 . However, due to the appraisal proceedings that have been initiated in accordance with applicable German law, this time period for tendering shares has been extended pursuant to the German Stock Corporation Act (Aktiengesetz) and will end two months after the date on which a final decision in such appraisal proceedings has been published in the Federal Gazette (Bundesanzeiger). We are also obligated to absorb any annual net loss of Adtran Networks under the DPLTA. Additionally, our obligation to pay Annual Recurring Compensation under the DPLTA is a continuing payment obligation, which will amount to approximately € 8.9 million (or $ 10.0 millio n based on the current exchange rate) per year assuming none of the minority Adtran Networks shareholders as of September 30, 2024 were to elect Exit Compensation. The foregoing amounts do not reflect any potential increase in payment obligations that we may have depending on the outcome of ongoing appraisal proceedings in Germany. The Annual Recurring Compensation is due on the third banking day following the ordinary general shareholders’ meeting of Adtran Networks for the respective preceding fiscal year (but in any event within eight months following expiration of the fiscal year). With respect to the 2023 fiscal year, Adtran Networks’ ordinary general shareholders’ meeting occurred on June 28, 2024 and, therefore, the Annual Recurring Compensation was paid on July 3, 2024. During the three months ended September 30, 2024 and 2023, we accrued $ 2.4 million and $ 2.6 million, respectively, in Annual Recurring Compensation. During the nine months ended September 30, 2024 and 2023, we accrued $ 7.4 million and $ 7.6 million, respectively, in Annual Recurring Compensation. The Annual Recurring Compensation is reflected as an increase to retained deficit in the Condensed Consolidated Balance Sheets. On October 18, 2022, the Company's Board of Directors authorized the Company to purchase additional shares of Adtran Networks through open market purchases not to exceed 15,346,544 shares. For the three and nine months ended September 30, 2024, approximately 830 thousand shares and 831 thousand shares, respectively, of Adtran Networks stock were tendered to the Company. This resulted in total Exit Compensation payments of approximately € 15.7 million, or approximately $ 17.4 million , based on an exchange rate as of September 30, 2024, being paid to Adtran Networks shareholders. For the three and nine months ended September 30, 2023 , less than 1 thousand shares and 64 thousand shares, respectively, of Adtran Networks stock were tendered to the Company. This resulted in Exit Compensation payments of approximately € 8 thousand and € 1.1 million, respectively, or approximately $ 9 thousand and $ 1.2 million, respectively, based on an exchange rate as of September 30, 2023, being paid to Adtran Networks shareholders. On July 18, 2022, ADTRAN, Inc., as the borrower, and ADTRAN Holdings, Inc. entered into a credit agreement with a syndicate of banks, including Wells Fargo Bank, National Association, as administrative agent (“Administrative Agent”), and the other lenders named therein (“Credit Agreement”), which has since been amended four times. The Company had access to $ 205.6 million on its Credit Facility for future borrowings; however, as of September 30, 2024 , the Company was limited to additional borrowings of $ 24.1 million based on debt covenant compliance metrics. The financial covenants under the Credit Agreement, as amended, require the Company to maintain a Consolidated Total Net Leverage Ratio of 5.00 x, a Consolidated Senior Secured Net Leverage Ratio of 3.25 x ( 4.0 x to 3.5 x during a Springing Covenant Period) and a Consolidated Fixed Charge Coverage Ratio of 1.25 x. See Note 11, Revolving Credit Agreements for additional information regarding the terms of the Wells Fargo Credit Agreement and its amendments. As of September 30, 2024, and as of the date of issuance of these financial statements, the Company does not have sufficient liquidity to meet payment obligations under the DPLTA pertaining to Exit Compensation. While the Company did experience $17.4 million of redemptions in Q3 2024, we believe the probability that more than a small minority of Adtran Networks shareholders elect to receive Exit Compensation in the next twelve months is remote based on the following factors: (i) the diverse base of shareholders that must make this election on an individual shareholder basis, (ii) the fact that the Company expects to receive a procedural decision on a matter of law related to the current ongoing appraisal proceedings involving a dispute over the value of the Exit Compensation in 2024 or early 2025, after which the appeal process should take an additional 24-32 months to resolve, (iii) the current guaranteed Annual Recurring Compensation payment plus the interest earned on such shares during the ongoing appraisal proceedings, and (iv) the current trading value of Adtran Networks shares. The Company experienced revenue declines in the year ended December 31, 2023, and during the three and nine months ended September 30, 2024. To the extent the Company does not experience anticipated revenue growth, the Company will implement plans to preserve cash liquidity and maintain compliance with the Company’s net leverage covenants. The Company has suspended dividend payments and has implemented a business efficiency program, which includes, but is not limited to ongoing reductions in operating expenses and a site consolidation plan. In connection with the site consolidation plan, the Company is also exploring a potential sale of portions of our headquarters in Huntsville. There can be no assurance that the Company will be successful in effecting this action on commercially reasonable terms or at all. We may need to further reduce capital expenditure and/or take other steps to preserve working capital in order to ensure that we can meet our needs and obligations and maintain compliance with our net leverage debt covenants. In summary, the Company believes that its cash and cash equivalents, investments, working capital management initiatives and availability to access cash under the Wells Fargo credit facility will be adequate to meet our business operating requirements, our capital expenditures and our expected obligations under the DPLTA, including anticipated levels of Exit Compensation and to support our ability to continue to comply with our debt covenants under the Credit Facility, for at least the next twelve months, from the issuance of these financial statements. See Note 11, Revolving Credit Agreements, for additional information regarding the terms of the Amendments of the Wells Fargo Credit agreement. 1. SUMMARY OF SIGNIFICANT ACCOUNTING POLICIES Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements of ADTRAN Holdings, Inc. and its subsidiaries have been prepared pursuant to the rules and regulations of the SEC applicable to interim financial information presented in Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by generally accepted accounting principles in the United States of America (“U.S. GAAP”) for complete financial statements are not included herein. The December 31, 2023, Condensed Consolidated Balance Sheet is derived from audited financial statements but does not include all disclosures required by U.S. GAAP for annual financial statements. 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 Holdings, Inc. Annual Report on Form 10-K for the year ended December 31, 2023 , filed with the SEC on March 15, 2024. Revision of Previously Issued Condensed Consolidated Financial Statements Following the third quarter of 2024, the Company identified errors primarily impacting the carrying values of the redeemable non-controlling interest, retained deficit, the net income attributable to the non-controlling interest and the net loss attributable to the Company and, as a consequence, of the loss per common share attributable to the Company. The Company has evaluated the errors and determined that the related impacts were not material to the previously issued consolidated financial statements for any prior period. A summary of the corrections to the Company's Condensed Consolidated Financial Statements for the periods ended March 31, 2023, June 30, 2023, September 30, 2023, December 31, 2023, March 31, 2024 and June 30, 2024, are as follows: (a) Pursuant to the terms of the DPLTA, each Adtran Networks shareholder (other than the Company) is entitled to receive from us an Annual Recurring Compensation payment of € 0.52 per share. The Company erroneously accrued this liability every quarter at € 0.59 per share, overstating the associated accrual, the net income attributable to non-controlling interest and the net loss attributable to ADTRAN Holdings, Inc. for fiscal periods beginning with the quarter ended March 31, 2023 through the quarter ended June 30, 2024. (b) For the periods beginning with the quarter ended March 31, 2023 through the quarter ended June 30, 2024 the Company remeasured the redeemable non-controlling interest each quarter-end at the current exchange rate of Euros to U.S. Dollar. The Company treated the redeemable non-controlling interest as a monetary mezzanine equity instrument but should have treated it as a non-monetary mezzanine equity instrument not subject to remeasurement. We have revised our previously issued Condensed Consolidated Financial Statements for the periods ended March 31, 2023, June 30, 2023, September 30, 2023, December 31, 2023, March 31, 2024 and June 30, 2024. Additionally, the Company will revise its previously issued 2023 interim financial statements and 2023 annual financial statements in connection with the future filings of the Form 10-K for the year ended December 31, 2024, and interim reporting on Form 10-Q for the periods ended March 31, 2025 and June 30, 2025. The following tables reflect the impact of the revision to the specific line items presented in the Company's previously reported Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Loss, and Condensed Consolidated Statements of Comprehensive Loss for the for fiscal periods beginning with the quarter ended March 31, 2023 through the quarter ended June 30, 2024. March 31, 2023 (In thousands) As Previously Reported Revision As Revised Other non-current liabilities $ 15,986 $ ( 346 ) (a) $ 15,640 Total Liabilities $ 675,765 $ (346 ) $ 675,419 Redeemable Non-Controlling Interest $ 442,668 $ ( 430 ) (b) $ 442,238 Accumulated Other Comprehensive Income $ 34,526 $ 1 (a) $ 34,527 Retained Earnings $ 8,006 $ 775 (a)(b) $ 8,781 Total Equity $ 820,162 $ 776 $ 820,938 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,938,595 $ — $ 1,938,595 For the Three Months Ended March 31, 2023 (In thousands) As Previously Reported Revision As Revised Less: Net Loss attributable to non-controlling interest $ ( 370 ) $ ( 345 ) (a) $ ( 715 ) Net Loss attributable to ADTRAN Holdings, Inc. $ ( 40,083 ) $ 345 (a) $ ( 39,738 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.51 ) $ — $ ( 0.51 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.51 ) $ — $ ( 0.51 ) Foreign currency translation gain $ 8,678 $ 1 (a) $ 8,679 Other Comprehensive Income, net of tax $ 8,782 $ 1 $ 8,783 Comprehensive Loss, net of tax $ ( 31,671 ) $ 1 $ ( 31,670 ) Less: Comprehensive Income (Loss) attributable to non-controlling interest, net of tax $ 12 $ ( 345 ) (a) $ ( 333 ) Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 31,683 ) $ 346 (a) $ ( 31,337 ) June 30, 2023 (In thousands) As Previously Reported Revision As Revised Other non-current liabilities $ 16,401 $ ( 695 ) (a) $ 15,706 Total Liabilities $ 665,006 $ (695 ) $ 664,311 Redeemable Non-Controlling Interest $ 445,462 $ ( 3,244 ) (b) $ 442,218 Accumulated Other Comprehensive Income $ 41,483 $ 2 (a) $ 41,485 Retained Deficit $ ( 41,010 ) $ 3,937 (a)(b) $ ( 37,073 ) Total Equity $ 782,470 $ 3,939 $ 786,409 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,882,938 $ — $ 1,882,938 For the Three Months Ended June 30, 2023 For the Six Months Ended June 30, 2023 (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,882 $ ( 348 ) (a) $ 2,534 $ 2,512 $ ( 693 ) (a) $ 1,819 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 39,097 ) $ 348 (a) $ ( 38,749 ) $ ( 79,180 ) $ 693 (a) $ ( 78,487 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.50 ) $ — $ ( 0.50 ) $ ( 1.01 ) $ 0.01 (a) $ ( 1.00 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.50 ) $ — $ ( 0.50 ) $ ( 1.01 ) $ 0.01 (a) $ ( 1.00 ) Foreign currency translation gain $ 6,940 $ 1 (a) $ 6,941 $ 15,618 $ 2 (a) $ 15,620 Other Comprehensive Income, net of tax $ 6,957 $ 1 $ 6,958 $ 15,739 $ 2 $ 15,741 Comprehensive Loss, net of tax $ ( 29,258 ) $ 1 $ ( 29,257 ) $ ( 60,929 ) $ 2 $ ( 60,927 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,882 $ ( 348 ) (a) $ 2,534 $ 2,894 $ ( 693 ) (a) $ 2,201 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 32,140 ) $ 349 (a) $ ( 31,791 ) $ ( 63,823 ) $ 695 (a) $ ( 63,128 ) September 30, 2023 (In thousands) As Previously Reported Revision As Revised Other non-current liabilities $ 17,408 $ ( 1,049 ) (a) $ 16,359 Total Liabilities $ 625,355 $ (1,049 ) $ 624,306 Redeemable Non-Controlling Interest $ 431,921 $ 10,291 (b) $ 442,212 Accumulated Other Comprehensive Income $ 12,075 $ 3 (a) $ 12,078 Retained Deficit $ ( 113,289 ) $ ( 9,245 ) (a)(b) $ ( 122,534 ) Total Equity $ 684,893 $ ( 9,242 ) $ 675,651 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,742,169 $ — $ 1,742,169 For the Three Months Ended September 30, 2023 For the Nine Months Ended September 30, 2023 (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,914 $ ( 353 ) (a) $ 2,561 $ 5,426 $ ( 1,046 ) (a) $ 4,380 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 78,563 ) $ 353 (a) $ ( 78,210 ) $ ( 157,743 ) $ 1,046 (a) $ ( 156,697 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 1.00 ) $ — $ ( 1.00 ) $ ( 2.01 ) $ 0.01 (a) $ ( 2.00 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 1.00 ) $ — $ ( 1.00 ) $ ( 2.01 ) $ 0.01 (a) $ ( 2.00 ) Foreign currency translation loss $ ( 29,716 ) $ 1 (a) $ ( 29,715 ) $ ( 14,098 ) $ 3 (a) $ ( 14,095 ) Other Comprehensive Loss, net of tax $ ( 29,408 ) $ 1 $ ( 29,407 ) $ ( 13,669 ) $ 3 $ ( 13,666 ) Comprehensive Loss, net of tax $ ( 105,057 ) $ 1 $ ( 105,056 ) $ ( 165,986 ) $ 3 $ ( 165,983 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,914 $ ( 353 ) (a) $ 2,561 $ 5,808 $ ( 1,046 ) (a) $ 4,762 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 107,971 ) $ 354 (a) $ ( 107,617 ) $ ( 171,794 ) $ 1,049 (a) $ ( 170,745 ) March 31, 2024 (In thousands) As Previously Reported Revision As Revised Accrued Expenses and Other Liabilities $ 36,404 $ ( 1,403 ) (a) $ 35,001 Total Current Liabilities $ 282,746 $ (1,403 ) $ 281,343 Other non-current liabilities $ 35,375 $ (350 ) (a) $ 35,025 Total Liabilities $ 620,488 $ (1,753 ) $ 618,735 Redeemable Non-Controlling Interest $ 441,635 $ 511 (b) $ 442,146 Accumulated Other Comprehensive Income $ 29,656 $ 5 (a) $ 29,661 Retained Deficit $ ( 558,363 ) $ 1,237 (a)(b) $ ( 557,126 ) Total Equity $ 265,783 $ 1,242 $ 267,025 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,327,906 $ — $ 1,327,906 For the Three Months Ended March 31, 2024 (In thousands) As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,880 $ ( 349 ) (a) $ 2,531 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 324,550 ) $ 349 (a) $ ( 324,201 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 4.12 ) $ — $ ( 4.12 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 4.12 ) $ — $ ( 4.12 ) Foreign currency translation loss $ ( 17,745 ) $ 1 (a) $ ( 17,744 ) Other Comprehensive Loss, net of tax $ ( 17,805 ) $ 1 $ ( 17,804 ) Comprehensive Loss, net of tax $ ( 339,475 ) $ 1 $ ( 339,474 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,880 $ ( 349 ) (a) $ 2,531 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 342,355 ) $ 350 (a) $ ( 342,005 ) June 30, 2024 (In thousands) As Previously Reported Revision As Revised Accrued Expenses and Other Liabilities $ 36,307 $ ( 1,403 ) (a) $ 34,904 Total Current Liabilities $ 289,712 $ (1,403 ) $ 288,309 Other non-current liabilities $ 34,445 $ (701 ) (a) $ 33,744 Total Liabilities $ 630,810 $ (2,104 ) $ 628,706 Redeemable Non-Controlling Interest $ 439,743 $ 2,379 (b) $ 442,122 Accumulated Other Comprehensive Income $ 28,274 $ 6 (a) $ 28,280 Retained Deficit $ ( 606,375 ) $ ( 281 ) (a)(b) $ ( 606,656 ) Total Equity $ 220,229 $ ( 275 ) $ 219,954 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,290,782 $ — $ 1,290,782 For the Three Months Ended June 30, 2024 For the Six Months Ended June 30, 2024 (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,854 $ ( 350 ) (a) $ 2,504 $ 5,734 $ ( 699 ) (a) $ 5,035 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 49,865 ) $ 350 (a) $ ( 49,515 ) $ ( 374,415 ) $ 699 (a) $ ( 373,716 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.63 ) $ — $ ( 0.63 ) $ ( 4.75 ) $ 0.01 (a) $ ( 4.74 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.63 ) $ — $ ( 0.63 ) $ ( 4.75 ) $ 0.01 (a) $ ( 4.74 ) Foreign currency translation loss $ ( 1,375 ) $ 1 (a) $ ( 1,374 ) $ ( 19,120 ) $ 2 (a) $ ( 19,118 ) Other Comprehensive Loss, net of tax $ ( 1,382 ) $ 1 $ ( 1,381 ) $ ( 19,187 ) $ 2 $ ( 19,185 ) Comprehensive Loss, net of tax $ ( 48,393 ) $ 1 $ ( 48,392 ) $ ( 387,868 ) $ 2 $ ( 387,866 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,854 $ ( 350 ) (a) $ 2,504 $ 5,734 $ ( 699 ) (a) $ 5,035 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 51,247 ) $ 351 (a) $ ( 50,896 ) $ ( 393,602 ) $ 701 (a) $ ( 392,901 ) The following tables reflect the impact of the revisions to the specific line items presented in the Company’s previously reported Consolidated Balance Sheet as of December 31, 2023, the Consolidated Statement of Loss and the Consolidated Statement of Comprehensive Loss for the year ended December 31, 2023. December 31, 2023 (In thousands) As Previously Reported Revision As Revised Accrued Expenses and Other Liabilities $ 37,607 $ ( 1,403 ) (a) $ 36,204 Total Current Liabilities $ 279,511 $ (1,403 ) $ 278,108 Total Liabilities $ 636,934 $ (1,403 ) $ 635,531 Redeemable Non-Controlling Interest $ 451,756 $ ( 9,604 ) (b) $ 442,152 Accumulated Other Comprehensive Income $ 47,461 $ 4 (a) $ 47,465 Retained Deficit $ ( 243,908 ) $ 11,003 (a)(b) $ ( 232,905 ) Total Equity $ 593,822 $ 11,007 $ 604,829 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,682,512 $ — $ 1,682,512 For the Year Ended December 31, 2023 (In thousands) As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 8,345 $ ( 1,399 ) (a) $ 6,946 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 267,688 ) $ 1,399 (a) $ ( 266,289 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 3.41 ) $ 0.02 (a) $ ( 3.39 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 3.41 ) $ 0.02 (a) $ ( 3.39 ) Foreign currency translation gain $ 22,753 $ 4 (a) $ 22,757 Other Comprehensive Income, net of tax $ 21,717 $ 4 $ 21,721 Comprehensive Loss, net of tax $ ( 237,626 ) $ 4 $ ( 237,622 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 8,727 $ ( 1,399 ) (a) $ 7,328 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 246,353 ) $ 1,403 (a) $ ( 244,950 ) The following tables reflect the impact of the revision to the specific line items presented in the Company's previously reported Condensed Consolidated Statements of Changes in Stockholders Equity as of September 30, 2023 and 2024: Retained Earnings (Deficit) Accumulated Other Comprehensive Income (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Annual recurring compensation earned $ ( 2,809 ) $ 345 (a) $ ( 2,464 ) $ - $ - $ - Other comprehensive income, net of tax $ - $ - $ - $ 8,400 $ 1 (a) $ 8,401 Foreign currency remeasurement of redeemable non-controlling interest $ ( 430 ) $ 430 (b) $ - $ - $ - $ - Balance as of March 31, 2023 $ 8,006 $ 775 $ 8,781 $ 34,526 $ 1 $ 34,527 Annual recurring compensation earned $ ( 2,882 ) $ 348 (a) $ ( 2,534 ) $ - $ - $ - Other comprehensive income, net of tax $ - $ - $ - $ 6,957 $ 1 (a) $ 6,958 Foreign currency remeasurement of redeemable non-controlling interest $ ( 2,814 ) $ 2,814 (b) $ - $ - $ - $ - Balance as of June 30, 2023 $ ( 41,010 ) $ 3,937 $ ( 37,073 ) $ 41,483 $ 2 $ 41,485 Annual recurring compensation earned $ ( 2,914 ) $ 353 (a) $ ( 2,561 ) $ - $ - $ - Other comprehensive loss, net of tax $ - $ - $ - $ ( 29,408 ) $ 1 (a) $ ( 29,407 ) Foreign currency remeasurement of redeemable non-controlling interest $ 13,535 $ ( 13,535 ) (b) $ - $ - $ - $ - Balance as of September 30, 2023 $ ( 113,289 ) $ ( 9,245 ) $ ( 122,534 ) $ 12,075 $ 3 $ 12,078 Retained Deficit Accumulated Other Comprehensive Income (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Balance as of December 31, 2023 $ ( 243,908 ) $ 11,003 (a) $ ( 232,905 ) $ 47,461 $ 4 (a) $ 47,465 Annual recurring compensation earned $ ( 2,880 ) $ 349 (a) $ ( 2,531 ) $ - $ - $ - Other comprehensive loss, net of tax $ - $ - $ - $ ( 17,805 ) $ 1 (a) $ ( 17,804 ) Foreign currency remeasurement of redeemable non-controlling interest $ 10,115 $ ( 10,115 ) (b) $ - $ - $ - $ - Balance as of March 31, 2024 $ ( 558,363 ) $ 1,237 $ ( 557,126 ) $ 29,656 $ 5 $ 29,661 Annual recurring compensation earned $ ( 2,854 ) $ 350 (a) $ ( 2,504 ) $ - $ - Other comprehensive loss, net of tax $ - $ - $ - $ ( 1,382 ) $ 1 (a) $ ( 1,381 ) Foreign currency remeasurement of redeemable non-controlling interest $ 1,868 $ ( 1,868 ) (b) $ - $ - $ - $ - Balance as of June 30, 2024 $ ( 606,375 ) $ ( 281 ) $ ( 606,656 ) $ 28,274 $ 6 $ 28,280 The following tables reflect the impact of the revision to the specific line items presented in the Company's previously reported Consolidated Statement of Changes in Stockholders as of December 31, 2023: Retained Earnings (Deficit) Accumulated Other Comprehensive Income (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Annual recurring compensation earned $ ( 11,524 ) $ 1,399 (a) $ ( 10,125 ) $ - $ - $ - Other comprehensive income, net of tax $ - $ - $ - $ 21,335 $ 4 (a) $ 21,339 Foreign currency remeasurement of redeemable non-controlling interest $ ( 9,604 ) $ 9,604 (b) $ - $ - $ - $ - Balance as of December 31, 2023 $ ( 243,908 ) $ 11,003 $ ( 232,905 ) $ 47,461 $ 4 $ 47,465 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 allowance for credit losses on accounts receivable and contract assets, 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 revenue 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, estimates of intangible assets upon measurement, estimated pension liability and fair value of investments and estimated contingent liabilities. 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 ongoing inflationary pressures, continued elevated interest rates, instability in the financial services industry, currency fluctuations and political tensions as of September 30, 2024, and through the date of this report. These conditions could result in further impacts to the Company's consolidated financial statements in future reporting periods. 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 as sets, revenue recognition and costs of revenue. Accounts Receivable Factoring Receivables Purchase Agreement On July 1, 2024, the Company entered into a receivables purchase agreement (the “Factoring Agreement”) with a third-party financial institution (the “Factor”), which accelerates receivable collection and helps to better manage cash flow. These transactions are accounted for in accordance with ASC Topic 860 and result in a reduction in accounts receivable because the Factoring Agreement transfers effective control over, and risk related to the receivables to the buyers. Trade accounts receivables balances sold are removed from the Condensed Consolidated Balance Sheets and cash received is reflected as cash flows provided by (used in) operating activities in the Condensed Consolidated Statements of Cash Flow. Factoring related interest expense is recorded to interest expense on the Condensed Consolidated Statements of Loss. On each sale date, the Factor retains from the sale price a default reserve, up to a required balance, which is held by the Factor in a reserve account and pledged to the Company. The Factor is entitled to withdraw from the reserve account the sale price of a defaulted receivable. The balance in the reserve account is included in other assets on the Condensed Consolidated Balance Sheets. Previous Receivables Purchase Agreement On December 19, 2023, the Company entered into a receivables purchase agreement (the “Prior Factoring Agreement”) with a third-party financial institution and was terminated on July 1, 2024. The Prior Factoring Agreement qualified for treatment as a secured borrowing with a pledge of collateral under Accounting Standards Codification ("ASC") Topic 810, Consolidations, as the Company was considered the primary beneficiary in a variable interest e

Revenue

Revenue	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Revenue	2. REVENUE The following is a description of the principal activities from which revenue is generated by reportable segment: Network Solutions Segment - Includes hardware and software products that enable a digital future which support the Company's Subscriber, Access & Aggregation, and Optical Networking Solutions. Services & Support Segment - Includes network design, implementation, maintenance and cloud-hosted services supporting the Company's Subscriber, Access & Aggregation, and Optical Networking Solutions. Revenue by Category In addition to the Company's reportable segments, revenue is also reported for the following three categories – Subscriber Solutions, Access & Aggregation Solutions and Optical Networking Solutions. Our Subscriber Solutions portfolio is used by Service Providers to terminate their access services infrastructure at the customer premises while providing an immersive and interactive experience for residential, business and wholesale subscribers. This revenue category includes hardware- and software-based products and services. These solutions include fiber termination solutions for residential, business and wholesale subscribers, Wi-Fi access solutions for residential and business subscribers, Ethernet switching and network edge virtualization solutions for business subscribers, and cloud software solutions covering a mix of subscriber types. Our Optical Networking Solutions are used by communications Service Providers, internet content providers and large-scale enterprises to securely interconnect metro and regional networks over fiber. This revenue category includes hardware- and software-based products and services. Our solutions within this category include open optical terminals, open line systems, optical subsystems and modules, network infrastructure assurance systems, and automation platforms that are used to build high-scale, secure and assured optical networks. Our Access & Aggregation Solutions are solutions that are used by communications Service Providers to connect residential subscribers, business subscribers and mobile radio networks to the Service Providers’ metro network, primarily through fiber-based connectivity. This revenue category includes hardware- and software-based products and services. Our solutions within this category are a mix of fiber access and aggregation platforms, precision network synchronization and timing solutions, and access orchestration solutions that ensure highly reliable and efficient network performance. The following tables disaggregate revenue by reportable segment and revenue category: Three Months Ended September 30, 2024 September 30, 2023 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Subscriber Solutions $ 81,060 $ 9,036 $ 90,096 $ 52,921 $ 8,564 $ 61,485 Optical Networking Solutions 47,474 23,061 70,535 94,592 21,608 116,200 Access & Aggregation Solutions 52,954 14,119 67,073 81,051 13,595 94,646 Total $ 181,488 $ 46,216 $ 227,704 $ 228,564 $ 43,767 $ 272,331 Nine Months Ended September 30, 2024 September 30, 2023 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Subscriber Solutions $ 215,044 $ 27,218 $ 242,262 $ 196,726 $ 25,760 $ 222,486 Optical Networking Solutions 152,068 67,246 219,314 342,390 64,562 406,952 Access & Aggregation Solutions 174,843 43,449 218,292 254,868 39,315 294,183 Total $ 541,955 $ 137,913 $ 679,868 $ 793,984 $ 129,637 $ 923,621 The aggregate amount of transaction price allocated to remaining performance obligations that have not been satisfied as of September 30, 2024, related to contractual maintenance agreements, contractual SaaS and subscription services, and hardware contracts that exceed one year in duration amounte d to $ 280.8 million. As of September 30, 2024 , approximately 66.0 % is expected to be recognized over the next 12 months and the remainder recognized thereafter. The majority of the Company's remaining performance obligations as of September 30, 2024, are related to contracts or orders that have an original expected duration of one year or less 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 accounts receivable, contract assets and unearned revenue from contracts with customers: As of As of (In thousands) September 30, 2024 December 31, 2023 Accounts receivable, net $ 172,025 $ 216,445 Contract assets (1) $ 668 $ 691 Unearned revenue $ 54,615 $ 46,731 Non-current unearned revenue $ 24,901 $ 25,109 (1) Included in other receivables on the Condensed Consolidated Balance Sheets. Accounts Receivable The allowance for credit losses was $ 0.4 million as of September 30, 2024, and December 31, 2023, respectively, related to accounts receivable. Receivables Purchase Agreement On July 1, 2024, the Company entered into a receivables purchase agreement (the “Factoring Agreement”) with a third-party financial institution (the “Factor”), which accelerates receivable collection and helps to better manage cash flow. Total accounts receivables factored as of the end of September 30, 2024, totaled $ 16.7 million of which $ 3.7 million was retained pursuant to the Factoring Agreement in the reserve account. The Factoring Agreement provides for up to $ 40.0 million in factoring capacity, subject to eligible receivables and reserve requirements, secured by the receivables. The balance in the reserve account is included in other assets on the Condensed Consolidated Balance Sheets. The cost of the Factoring Agreement is included in interest expense in the Condensed Consolidated Statements of Loss and totaled $ 0.3 million for the three months and nine months ended September 30, 2024. Costs of a previous receivables purchase agreement which are included in interest expense in the Condensed Consolidated Statements of Loss totaled $ 0.3 million and $ 0.9 million for the three and nine months ended September 30, 2023. Previous Receivable Purchase Agreement On December 19, 2023, the Company entered into a receivables purchase agreement (the “Prior Factoring Agreement”) with a third-party financial institution (the "Factor") to replace a prior accounts receivable purchase agreement and to sell, on a revolving basis, undivided interests in the Company’s accounts receivable. The prior factoring agreement provided for up to $ 40.0 million in borrowing capacity, subject to eligible receivables and reserve requirements, secured by the receivables. The prior factoring agreement qualified for treatment as a secured borrowing with a pledge of collateral under Accounting Standards Codification ("ASC") Topic 810, Consolidations . The receivables purchase agreement was terminated on July 1, 2024 and there were no secured borrowings under this agreement as of September 30, 2024. Total secured borrowings under the agreement were $ 14.3 million as of December 31, 2023, which left $ 25.4 million available for future borrowings as of December 31, 2023. Accounts receivable pledged as collateral related to the secured borrowings were $ 16.8 million as of December 31, 2023. For the nine months ended September 30, 2024, the Company incurred program fee expenses of $ 0.6 million. Contract Assets No allowance for credit losses was recorded for the three and nine months ended September 30, 2024 and 2023, respectively, related to contract assets. Unearned Revenue Of the outstanding unearned revenue balances as of December 31, 2023 , $ 10.03 million and $ 43.1 million were recognized as revenue during the three and nine months ended September 30, 2024 , respectively. Of the $ 60.4 million of outstanding unearned revenue balances as of December 31, 2022, $ 6.1 million and $ 31.3 million were recognized as revenue during the three and nine months ended September 30, 2023 , respectively.

Income Taxes

Income Taxes	9 Months Ended
	Sep. 30, 2024
Income Tax Disclosure [Abstract]
Income Taxes	3. INCOME TAXES The Company’s effective tax rate changed from a benefit of 18.0 % of pre-tax loss for the three months ended September 30, 2023 , to a expense of 1.4 % of pre-tax loss for the three months ended September 30, 2024 , and changed from a benefit of 19.2 % of pre-tax loss for the nine months ended September 30, 2023 , to a benefit of 3.9 % of pre-tax loss for the nine months ended September 30, 2024. The change in the effective tax rate for the three and nine months ended September 30, 2024, was driven primarily by non-deductible impairment charges and a loss jurisdiction for which no tax benefits were recognized on its pre-tax losses incurred during the nine months ended September 30, 2024. 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 September 30, 2024 , the Company had net deferred tax assets totaling $ 91.3 million, and a valuation allowance totaling $ 87.1 million against those deferred tax assets. 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.

Stock-Based Compensation

Stock-Based Compensation	9 Months Ended
	Sep. 30, 2024
Share-Based Payment Arrangement [Abstract]
Stock-Based Compensation	4. STOCK-BASED COMPENSATION 2024 Stock Incentive Plans At the annual meeting of stockholders held on May 8, 2024, the Company’s stockholders approved, upon recommendation of the Board of Directors, the adoption of the ADTRAN Holdings, Inc. 2024 Employee Stock Incentive Plan (“2024 Employee Plan”) and the ADTRAN Holdings, Inc. 2024 Directors Stock Plan (“2024 Directors Plan”). No additional awards will be granted under the Company’s previous stock incentive plans, including the 2020 Employee Stock Incentive Plan, the 2020 Directors Stock Plan, or the 2015 Employee Stock Incentive Plan. Outstanding awards granted under the Company's prior equity incentive plans will remain subject to the terms of such applicable plans, and shares under such plans that are cancelled or forfeited will be available for issuance under the 2024 Employee Plan or the 2024 Directors Plan, as applicable. Under the 2024 Employee Plan, the Company is authorized to issue 4.0 million shares of common stock to certain employees, key service providers and advisors through incentive stock options and non-qualified stock options, stock appreciation rights, RSUs and restricted stock, any of which may be subject to performance-based conditions. RSUs and restricted stock granted under the 2024 Employee Plan will typically vest pursuant to a four-year vesting schedule beginning on the first anniversary of the grant date. Stock options granted under the 2024 Employee Plan will typically become exercisable beginning after one year of continued employment, normally pursuant to a four-year vesting schedule beginning on the first anniversary of the grant date and have a ten-year contractual term. Stock options, RSUs and restricted stock granted under the 2024 Employee Plan reduce the shares authorized for issuance under the 2024 Employee Plan by one share of common stock for each share underlying the award. Forfeitures, cancellations and expirations of awards granted under the prior employee stock incentive plans increase the shares authorized for issuance under the 2024 Employee Plan by one share of common stock for each share underlying the award. Under the 2024 Directors Plan, the Company is authorized to issue 0.7 million shares of common stock through stock options, restricted stock and RSUs to non-employee directors. Stock awards issued under the 2024 Directors Plan typically will become vested in full on the first anniversary of the grant date. Stock options issued under the 2024 Directors Plan will have a ten-year contractual term. Stock options, restricted stock and RSUs granted under the 2024 Directors Plan reduce the shares authorized for issuance under the 2024 Directors Plan by one share of common stock for each share underlying the award. Forfeitures, cancellations and expirations of awards granted under the prior directors stock plan increase the shares authorized for issuance under the 2024 Directors Plan by one share of common stock for each share underlying the award. As of September 30, 2024, 4.7 million shares were available for issuance pursuant to awards that may be made in the future under shareholder-approved equity plans. For the three months ended September 30, 2024 and 2023 , stock-based compensation expense was $ 3.6 million and $ 4.2 million, respectively, and for the nine months ended September 30, 2024 and 2023 , stock-based compensation expense was $ 11.4 million and $ 12.2 million, respectively. PSUs, RSUs and Restricted Stock - ADTRAN Holdings, Inc. The following table summarizes the PSUs, RSUs and restricted stock outstanding as of December 31, 2023, and September 30, 2024 and the changes that occurred during the nine months ended September 30, 2024: Number of Weighted Avg. Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2023 1,942 $ 17.46 PSUs, RSUs and restricted stock granted 1,097 $ 7.85 PSUs, RSUs and restricted stock vested ( 263 ) $ 18.86 PSUs, RSUs and restricted stock forfeited ( 111 ) $ 14.25 Unvested PSUs, RSUs and restricted stock outstanding, September 30, 2024 2,665 $ 13.50 The fair value of PSUs with performance conditions, RSUs and restricted stock is equal to the closing price of the Company's stock on the date of grant. The fair value of PSUs with market conditions is calculated using a Monte Carlo simulation valuation method. As of September 30, 2024 , total unrecognized compensation expense related to non-vested portion of performance-based PSUs (considered probable), market-based PSUs, RSUs and restricted stock was approximately $ 13.3 million, which will be recognized over the remaining weighted-average period of 2.2 years. As of September 30, 2024 , there was $ 11.0 million of unrecognized compensation expense related to unvested performance-based PSUs (not-considered probable), which will be recognized over the remaining requisite service period of 1.3 years if achievement of the performance obligation becomes probable. Unrecognized compensation expense will be adjusted for actual forfeitures. Stock Options - ADTRAN Holdings, Inc. The following table summarizes the ADTRAN Holdings, Inc. stock options outstanding as of December 31, 2023, and September 30, 2024, and the changes that occurred during the nine months ended September 30, 2024: Number of Weighted Avg. Weighted Avg. Aggregate Stock options outstanding, December 31, 2023 3,894 $ 10.32 5.25 $ 3,087 Stock options exercised ( 36 ) $ 6.06 Stock options forfeited ( 171 ) $ 6.68 Stock options expired ( 243 ) $ 9.31 Stock options outstanding, September 30, 2024 3,444 $ 10.61 4.64 $ 829 Stock options exercisable, September 30, 2024 1,342 $ 12.63 1.11 $ — As of September 30, 2024 , there was $ 4.2 million of unrecognized compensation expense related to stock options which will be recognized over the remaining weighted-average period of 1.2 years. The determination of the fair value of stock options assumed or granted by ADTRAN was estimated using the Monte Carlo method and is affected by its stock price, as well as assumptions regarding a number of complex and subjective variables that may have a significant impact on the fair value estimate. The stock option pricing model requires the use of several assumptions that impact the fair value estimate. These variables include, but are not limited to, the volatility of the Company's stock price and employee exercise behaviors. 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 the Company's closing stock price on the last trading day of the quarter and the exercise price, multiplied by the number of in-the-money options) that would have been received by the option holders had all option holders exercised their options on September 30, 2024 . The amount of aggregate intrinsic value was $ 0.8 million as of September 30, 2024, which will change based on the fair market value of the Company's stock. The total pre-tax intrinsic value of options exercised during the nine months ended September 30, 2024 , and 2023 was $ 34 thousand and $ 0.2 million , respectively. During the three and nine months ended September 30, 2024, 0.1 million stock options vested. No stock options vested during the three and nine months ended September 30, 2023. Stock Options - Adtran Networks During the third quarter of 2024, all remaining Adtran Networks stock options were modified which resulted in the acceleration of vesting and conversion to liability based awards that were settled for cash totaling $ 0.2 million. As of September 30, 2024, Adtran Networks had no remaining vested or unvested stock option awards outstanding.

Investments

Investments	9 Months Ended
	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Investments	5. INVESTMENTS Debt Securities and Other Investments The Company did no t have any debt securities and other investments as of September 30, 2024. Realized gains and losses on sales of debt securities are computed under the specific identification method. The following tab le presents the gross realized gains and losses related to its debt securities: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Gross realized gain on debt securities $ — $ 5 $ — $ 9 Gross realized loss on debt securities — ( 317 ) — ( 355 ) Total loss recognized, net $ — $ ( 312 ) $ — $ ( 346 ) Realized and unrealized gains and losses related to marketable equity securities were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Unrealized gain (loss) on equity securities held $ 1,372 $ ( 1,130 ) $ 4,371 $ 1,404 Realized (loss) gain on equity securities sold 10 ( 1 ) 136 13 Total gain (loss) recognized, net $ 1,382 $ ( 1,131 ) $ 4,507 $ 1,417 Income generated from marketable equity securities was recorded as interest and dividend income in the Condensed Consolidated Statements of Loss. 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 and • 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 September 30, 2024 Using (In thousands) Fair Value Quoted Prices Significant Significant Unobservable Inputs Cash equivalents Money market funds $ 5,500 $ 5,500 $ — $ — Marketable equity securities Marketable equity securities – various industries 1,035 1,035 — — Deferred compensation plan assets 30,471 30,471 — — Total $ 37,006 $ 37,006 $ — $ — Fair Value Measurements as of December 31, 2023 Using (In thousands) Fair Value Quoted Prices Significant Significant Unobservable Inputs Cash equivalents Money market funds $ 5,302 $ 5,302 $ — $ — Marketable equity securities Marketable equity securities – various industries 905 905 — — Deferred compensation plan assets 26,838 26,838 — — Total $ 33,045 $ 33,045 $ — $ — 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.

Inventory

Inventory	9 Months Ended
	Sep. 30, 2024
Inventory Disclosure [Abstract]
Inventory	6. INVENTORY Inventory consisted of the following: As of As of (In thousands) September 30, 2024 December 31, 2023 Raw materials $ 114,873 $ 152,140 Work in process 10,942 17,239 Finished goods 157,111 192,916 Total inventory, net $ 282,926 $ 362,295 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. During the three and nine months ended September 30, 2024 , we renegotiated $ 0.3 million related to charges and an inventory write-down of $( 0.3 ) million and $ 8.6 million, respectively, as a result of a strategy shift which included discontinuance of certain product lines in connection with the Business Efficiency Program of which $ 4.1 million relates to inventory write-downs and $ 4.5 million relates to other charges all of which are included in cost of revenue in the Condensed Consolidated Statements of Loss. In connection with the Company’s restructuring efforts, during the quarter ended September 30, 2023, management determined that there would be a discontinuation of product lines in the Network solutions segment and, as a result, wrote-down related inventories of $ 21.0 million, which is included in cost of revenue in the Condensed Consolidated Statements of Loss.

Property, Plant and Equipment

Property, Plant and Equipment	9 Months Ended
	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	7. PROPERTY, PLANT AND EQUIPMENT Property, plant and equipment consisted of the following: As of As of (In thousands) September 30, 2024 December 31, 2023 Engineering and other equipment $ 187,753 $ 183,336 Building 79,857 79,215 Computer hardware and software 139,006 101,572 Building and land improvements 59,487 58,238 Furniture and fixtures 21,542 21,368 Land 5,248 5,242 Total property, plant and equipment 492,893 448,971 Less: accumulated depreciation ( 345,465 ) ( 325,951 ) Total property, plant and equipment, net $ 147,428 $ 123,020 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. Depreciation expense was $ 8.7 million and $ 7.4 million for the three months ended September 30, 2024 and 2023 , respectively, and $ 24.5 million and $ 22.6 million for the nine months ended September 30, 2024 and 2023 , 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.

Goodwill

Goodwill	9 Months Ended
	Sep. 30, 2024
Goodwill Disclosure [Abstract]
Goodwill	8. GOODWILL The changes in the carrying amount of goodwill for the nine months ended September 30, 2024, are as follows: (In thousands) Network Solutions Services & Support Total As of December 31, 2023 $ 297,031 $ 56,384 $ 353,415 Goodwill impairment ( 290,528 ) — ( 290,528 ) Foreign currency translation adjustments ( 6,503 ) 500 ( 6,003 ) As of September 30, 2024 $ — $ 56,884 $ 56,884 Goodwill represents the excess purchase price over the fair value of net assets acquired. The Company performs its annual goodwill impairment assessment on the first day of the fourth quarter. In addition, the Company performs an interim impairment assessment prior to our annual measurement date whenever events or changes in circumstances indicate that the carrying amount of such assets (or group of assets) may not be recoverable. During the third quarter of 2023, the Company identified a triggering event due to a decrease in the Company’s market capitalization and changes in projections (decrease in estimated cash flows). While the quantitative impairment analysis indicated that there was no impairment of Network Solutions goodwill, the Company determined that a $ 37.9 million non-cash impairment charge for goodwill was warranted for the Services & Support reporting unit. During the fourth quarter of 2023, the Company completed its annual impairment test. There were no significant market changes or changes to cash flow projections, as such no triggering event was identified during the fourth quarter of 2023. During the first quarter of 2024, qualitative factors such as a decrease in the Company’s market capitalization, lower service provider spending and delayed holding patterns of inventory with respect to customers caused us to reduce our forecasts, triggering a quantitative impairment assessment for our reporting units. The Company determined the fair value of each reporting unit using a combination of an income approach and a market-based peer group analysis. The significant inputs and assumptions used in the determination of the fair value of our reporting units based on future cash flows for the reporting units, requires significant judgment and the use of estimates and assumptions related to cash flow projections, discount rate, peer group determination and market multiple selection. The Company determined upon its quantitative impairment assessment to recognize a $ 292.6 million non-cash goodwill impairment charge for the Network Solutions reporting unit. The quantitative impairment analysis indicated there was no impairment of the Services & Support goodwill during the first quarter of 2024. No impairment of goodwill was recognized during the three months ended September 30, 2024. Goodwill impairment recognized during the nine months ended September 30, 2024 , was $ 292.6 million. Goodwill impairment recognized during the three and nine months ended September 30, 2023 , was $ 37.9 million. As of September 30, 2024 , accumulated goodwill impairment losses totaled $ 330.5 million. The Company will continue to monitor its stock price, operating results and other macroeconomic factors to determine if there is indication of a decline in fair value requiring an event driven assessment of the recoverability of its remaining goodwill prior to the annual assessment.

Intangible Assets

Intangible Assets	9 Months Ended
	Sep. 30, 2024
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Intangible Assets	9. INTANGIBLE ASSETS Intangible assets consisted of the following: As of September 30, 2024 As of December 31, 2023 (In thousands) Weighted Average Useful Life Gross Carrying Amount Accumulated Amortization Net Book Value Gross Carrying Amount Accumulated Amortization Net Book Value Developed technology 8.5 $ 332,245 $ ( 91,210 ) $ 241,035 $ 329,369 $ ( 61,271 ) $ 268,098 Customer relationships 10.9 $ 54,016 $ ( 18,461 ) $ 35,555 $ 54,856 $ ( 15,943 ) $ 38,913 Trade names 3.0 29,955 ( 24,993 ) 4,962 29,689 ( 16,379 ) 13,310 Backlog 1.6 57,905 ( 55,133 ) 2,772 57,391 ( 52,022 ) 5,369 Licensed technology 9.0 5,900 ( 4,288 ) 1,612 5,900 ( 3,797 ) 2,103 Licensing agreements 8.5 560 ( 398 ) 162 560 ( 368 ) 192 Patents 7.3 — — — 500 ( 500 ) — Total $ 480,581 $ ( 194,483 ) $ 286,098 $ 478,265 $ ( 150,280 ) $ 327,985 Intangible assets are reviewed for impairment whenever events and circumstances indicate impairment may have occurred. In connection with the preparation of the financial statements for each period in 2024 and 2023, the Company assessed impairment triggers related to intangible assets. No impairment losses related to intangible assets were recorded during the three and nine months ended September 30, 2024 and 2023. Amortization expense was $ 14.7 million and $ 16.5 million in the three months ended September 30, 2024 and 2023 , respectively, and $ 43.7 million and $ 68.8 million in the nine months ended September 30, 2024 and 2023, 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. Estimated future amortization expense of intangible assets is as follows: As of (In thousands) September 30, 2024 2024 $ 14,905 2025 47,737 2026 44,408 2027 43,018 2028 42,870 Thereafter 93,160 Total $ 286,098

Hedging

Hedging	9 Months Ended
	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Hedging	10. HEDGING The Company has certain forward rate agreements to hedge foreign currency exposure of expected future cash flows in foreign currency. The Company does not hold or issue derivative instruments for trading or other speculative purposes. Derivatives are initially recognized at fair value on the date a derivative contract is entered into and are subsequently re-measured to their fair value at the end of each reporting period. All changes in the fair value of derivative instruments are recognized as other (expense) income in the Consolidated Statements of Loss and are classified as Level II under the fair value hierarchy. The derivative instruments are not subject to master netting agreements and are not offset in the Consolidated Balance Sheets. We are exposed to risk from credit-related losses resulting from nonperformance by counterparties to our financial instruments. We perform credit evaluations of our counterparties under forward exchange contracts and expect all counterparties to meet their obligations. We have not experienced credit losses from our counterparties. As of September 30, 2024 , the Company had 41 forward rate contracts outstanding. Foreign Currency Hedging Arrangements On November 3, 2022, the Company entered into a euro/U.S. dollar forward contract arrangement ("Initial Forward") with Wells Fargo Bank, N.A. (“Hedge Counterparty”). The Initial Forward, which is governed by the provisions of an ISDA Master Agreement (including schedules thereto and transaction confirmations that supplement such agreement) entered into between the Company and the Hedge Counterparty, enabled the Company to convert a portion of its euro denominated payment obligations under the proposed DPLTA into U.S. Dollars. Under the Initial Forward, the Company agreed to exchange an aggregate notional amount of € 160.0 million converted to U.S. dollars at a daily fixed forward rate ranging from EUR/USD 0.98286 to 1.03290 . The aggregate amount of € 160.0 million was divided into eight quarterly tranches of € 20.0 million, which commenced in the fourth quarter of 2022. During the nine months ended September 30, 2024 , the Company settled three € 20.0 million forward contract tranches, leaving the remaining tranche of € 20.0 million to be settled in the fourth quarter of 2024. The Company, at its sole discretion, may exchange all or part of each tranche on any given day within the applicable quarter; provided, however, that it must exchange the full tranche by the end of such quarter. The Initial Forward may be accelerated or terminated early for a number of reasons, including but not limited to (i) non-payment by the Company or the Hedge Counterparty, (ii) breach of representation or warranty or covenant by either party or (iii) insolvency or bankruptcy of either party. On March 21, 2023, the Company entered into a euro/U.S. dollar forward contract arrangements (“Forward”) with the Hedge Counterparty. Under the Forward, which is governed by the provisions of an ISDA Master Agreement (including schedules thereto and transaction confirmations that supplement such agreement) entered into between the Company and the Hedge Counterparty, the Company exchanged an aggregate notional amount of € 160.0 million converted to U.S. dollars at an average rate of EUR/USD 1.085 . During the nine months ended September 30, 2024 , the Company settled three $ 20.0 million forward contract tranches, leaving the remaining tranche of $ 20.0 million to be settled in the fourth quarter of 2024. These forward contracts were executed to sell EUR and to buy USD and were entered into for the purpose of unwinding th e Initial Forward to buy EUR and to sell USD. The drawdown dates of the Initial Forward are set to the same date as the maturity of the offsetting Forward. The fair values of the Company's derivative instruments recorded in the Condensed Consolidated Balance Sheet as of September 30, 2024 and December 31, 2023 were as follows: (In thousands) Balance Sheet Location September 30, 2024 December 31, 2023 Derivatives Not Designated as Hedging Instruments (Level 2): Foreign exchange contracts – derivative assets Other receivables $ 1,712 $ 7,125 Foreign exchange contracts – derivative liabilities Accounts payable $ ( 1,030 ) $ ( 2,277 ) Total derivatives $ 682 $ 4,848 The change in the fair values of the Company's derivative instruments recorded in the Condensed Consolidated Statements of Loss during the three and nine months ended September 30, 2024 and 2023 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) Income Statement 2024 2023 2024 2023 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other (expense) income, net $ ( 411 ) $ 1,012 $ ( 380 ) $ 1,076

Credit Agreements

Credit Agreements	9 Months Ended
	Sep. 30, 2024
Debt Disclosure [Abstract]
Credit Agreements	11. CREDIT AGREEMENTS The carrying amounts of the Company's non-current revolving credit facility in its Condensed Consolidated Balance Sheets were as follows: As of As of (In thousands) September 30, 2024 December 31, 2023 Wells Fargo credit agreement $ 189,849 $ 195,000 Total non-current revolving credit facility $ 189,849 $ 195,000 As of September 30, 2024, the weighted average interest rate on our revolving credit agreements was 8.45 %. Wells Fargo Credit Agreement On July 18, 2022, ADTRAN, Inc., as the borrower ("U.S. Borrower"), and the Company entered into a credit agreement with a syndicate of banks, including Wells Fargo Bank, National Association, as administrative agent (“Administrative Agent”), and the other lenders named therein (as amended from time to time, the “Credit Agreement”). As of the date of this filing, the Credit Agreement allows for revolving credit borrowings of up to $ 400.0 million in aggregate principal amount ($ 100.0 million of which is available to Adtran Networks as borrower pursuant to the Subline (as defined and further described below). On August 9, 2023, ("First Amendment Effective Date") the Company and ADTRAN, Inc. entered into a First Amendment to Credit Agreement (“First Amendment”). The First Amendment, among other things, increased the available funding from $ 100.0 million to $ 400.0 million. In addition, a new $ 50.0 million delayed draw term loan facility (“DDTL”) was introduced, which (subject to certain conditions) was available for borrowing in the event that at least sixty percent ( 60.0 %) of the outstanding shares of Adtran Networks that were not owned by the Company and its subsidiaries as of the First Amendment Effective Date was tendered (such event, a “Springing Covenant Event”). Upon the occurrence of a Springing Covenant Event, the Company will enter a “Springing Covenant Period”, defined as the fiscal quarter in which a Springing Covenant Event occurs and the three (3) consecutive fiscal quarters thereafter. During the Springing Covenant Period, the Company’s leverage ratios are increased. Although the ability to borrow under the DDTL expired on August 9, 2024, the Springing Covenant Event and Springing Covenant Period remain in effect. The First Amendment further added additional financial flexibility by permitting, subject to certain requirements, the incurrence of convertible indebtedness by the Company in an aggregate principal amount of up to $ 172.5 million. Any such convertible indebtedness must, among other things, be incurred in pro forma compliance with the financial covenants in the Credit Agreement, be unsecured, and otherwise rank junior to borrowings under the Credit Agreement and have a stated maturity date of at least 91 days after the latest scheduled maturity date of loans and commitments under the Credit Agreement. Net cash proceeds from any incurrence of convertible indebtedness must be used to repurchase shares of Adtran Networks or repay revolver borrowings under the Credit Agreement. On January 16, 2024 ("Second Amendment Effective Date"), the Company and ADTRAN, Inc. entered into a Second Amendment to Credit Agreement and First Amendment to Collateral Agreement ("Second Amendment"). The Second Amendment, among other things, introduced the Covenant Relief Period, which provided the Company with additional covenant headroom while imposing a minimum liquidity financial covenant from the end of the fourth quarter of 2023 to the end of the third quarter of 2024. The Covenant Relief Period ended on November 7, 2024. On March 12, 2024, the Company and ADTRAN, Inc. entered into a Third Amendment to Credit Agreement ("Third Amendment"). The Third Amendment, among other things, amended the definition of “Consolidated Funded Indebtedness” (which is used in the calculation of the Consolidated Total Net Leverage Ratio and the Consolidated Senior Secured Net Leverage Ratio) to exclude obligations of the Company and its subsidiaries under certain factoring arrangements when calculated for the fiscal quarters ending March 31, 2024, and June 30, 2024. On June 4, 2024, the Company, ADTRAN, Inc., and Adtran Networks entered into a Fourth Amendment to Credit Agreement ("Fourth Amendment"). The Fourth Amendment, among other things, created a new sublimit under the existing $ 400.0 million revolving commitments, in an aggregate amount of $ 100.0 million (“Subline”), which Subline is available for borrowings by Adtran Networks. Prepayments of outstanding loans under the Subline that result in the remaining outstanding loans under the Subline being less than the German Commitment Reduction Threshold will result in a permanent partial reduction of the commitments in respect of the Subline. The German Commitment Reduction Threshold is initially $ 75.0 million and may be lowered from time to time pursuant to the terms of the Fourth Amendment. The existing swing line sublimit and letter of credit sublimit under the Credit Agreement remained available to the US Borrower (and not to Adtran Networks) after giving effect to the Fourth Amendment. Otherwise, the loans under the Subline are subject to substantially the same terms and conditions under the Credit Agreement (including with respect to the interest rate and maturity date) as the other existing revolving commitments. As of September 30, 2024 , ADTRAN, Inc.’s borrowings under the revolving line of credit were $ 189.8 million, of which approximately $ 115.0 million were borrowed by ADTRAN, Inc. and $ 75.0 million were borrowed under the Subline by Adtran Networks. The credit facilities provided under the Credit Agreement mature in July 2027, but the U.S. Borrower may request extensions subject to custo mary conditions. In addition, the U.S. Borrower may utilize up to $ 50.0 million of the $ 400.0 million total revolving facility for the issuance of letters of credit. As of September 30, 2024 , we had a total of $ 4.4 million in letters of credit under ADTRAN, Inc. outstanding under the Credit Agreement, leaving a net amount (after giving effect to the $ 189.8 million of outstanding borrowings described above) of $ 205.6 million available for future borrowings; however, as of September 30, 2024 , the Company was limited to additional borrowings of $ 24.1 million based on debt covenant compliance metrics. Any future credit extensions under the Credit Agreement are subject to customary conditions precedent. The proceeds of any loans are expected to be used for general corporate purposes and to pay a portion of the Exchange Offer consideration. As of September 30, 2024, the Company was in compliance with all covenants. Revolving Line of Credit Interest Rate All U.S. dollar borrowings under the revolving line of credit other than swingline loans, which bear interest at the Base Rate (as defined below plus the applicable margin), bear interest, at the Company’s option, at a rate per annum equal to either (A) the Base Rate plus an applicable margin ranging from 0.65 % to 1.65 % per annum based on the Company’s Consolidated Total Net Leverage Ratio (or, during the Applicable Margin Increase Period (as defined below), an applicable margin of 2.15 % per annum), or (B) Adjusted Term SOFR (as defined below) plus an applicable margin ranging from 1.65 % to 2.65 % per annum based on the Company’s Consolidated Total Net Leverage Ratio (or, during the Applicable Margin Increase Period, an applicable margin of 3.15 % per annum). “Base Rate” means the highest of (a) the federal funds rate (i.e., for any day, the rate per annum equal to the weighted average of the rates on overnight federal funds transactions with members of the Federal Reserve System, as published by the Federal Reserve Bank of New York on the business day next succeeding such day) plus ½ of 1.0 %, (b) the prime commercial lending rate of the Administrative Agent, as established from time to time at its principal U.S. office (which such rate is an index or base rate and will not necessarily be its lowest or best rate charged to its customers or other banks), or (c) the daily Adjusted Term SOFR (as defined in the Credit Agreement) for a one-month tenor plus 1.0 %. The Base Rate is subject to a floor of 1.00 % per annum. “Adjusted Term SOFR” means Term SOFR for the applicable interest period plus 0.10 % per annum. Adjusted Term SOFR is subject to a floor of 0.00 % per annum. All euro borrowings under the revolving line of credit bear interest at a rate per annum equal to EURIBOR (as defined in the Credit Agreement and subject to a 0.00 % per annum floor) plus an applicable margin ranging from 1.75 % to 2.75 % per annum based on the Company’s Consolidated Total Net Leverage Ratio (or, during the Applicable Margin Increase Period, an applicable margin of 3.25 % per annum). In addition, if on or prior to December 31, 2024, we have not reduced the aggregate revolving credit commitment to $ 340.0 million or less, the applicable margin for all loans shall be increased by 1.00 % per annum, and (y) if on or prior to June 30, 2025 we have not reduced the aggregate revolving credit commitment to $ 300.0 million or less, the applicable margin for all loans shall be increased by 1.00 % per annum. In addition to paying interest on outstanding principal under the Credit Agreement, the Company is required to pay a quarterly commitment fee to the lenders under the Credit Agreement in respect of unutilized revolving loan commitments on the average daily unused portion of the revolving credit commitment of each lender, which commitment fee ranges from 0.20 % to 0.25 % per annum based on the Company’s Consolidated Total Net Leverage Ratio (or, during the Applicable Margin Increase Period, is equal to 0.25 % per annum). The Company is also required to pay a participation fee to the Administrative Agent for the account of each lender with respect to the Company’s participation in letters of credit at the then applicable rate for Adjusted Term SOFR Loans or EURIBOR Loans, and other customary fronting, issuance and administration fees with respect to letters of credit. The “Applicable Margin Interest Period” means the period commencing on the Second Amendment Effective Date and ending on the first date when each of the following conditions have been met: (a) the Covenant Relief Period has ended, (b) since the Second Amendment Effective Date, the borrowers have repaid the revolving credit outstanding borrowings by a principal amount of at least $ 75.0 million, (c) the borrowers have reduced the aggregate revolving credit commitment to an amount no greater than $ 300.0 million, and (d) the borrowers are in compliance with all financial covenants based on the financial statements for the most recently completed reference period. Default interest is 2.0 % per annum in excess of the rate otherwise applicable. Covenants Under the Credit Agreement The financial covenants under the Credit Agreement, as amended, include the following (capitalized terms used in this subsection and not otherwise defined herein have the meanings assigned to them in the Credit Agreement or its amendments, as applicable): • As of the last day of any fiscal quarter, commencing with the fiscal quarter ended December 31, 2023, the Consolidated Total Net Leverage Ratio may not exceed 5.00 x. • As of the last day of any fiscal quarter, commencing with the fiscal quarter ended December 31, 2023, the Consolidated Senior Secured Net Leverage Ratio may not exceed: • In the fiscal quarter in which a Springing Covenant Event occurs and the three consecutive quarterly test periods thereafter, (“Springing Covenant Period”), the following covenant levels: • First fiscal quarter ending after a Springing Covenant Event: 4.00 x • Second fiscal quarter ending after a Springing Covenant Event: 3.75 x • Third and fourth fiscal quarters ending after a Springing Covenant Event: 3.50 x • If the Company or any of its subsidiaries incurs certain unsecured indebtedness in excess of $ 50.0 million in connection with a transaction that is a Springing Covenant Event or during a Springing Covenant Period, the Consolidated Senor Secured Net Leverage Ratio covenant will step down to 3.50 x at the time of such incurrence. • If a Springing Covenant Period is not in effect, the Consolidated Senior Secured Net Leverage Ratio may not exceed 3.25 x. • As of the last day of any fiscal quarter, commencing with the fiscal quarter ended December 31, 2023, the Consolidated Fixed Charge Coverage Ratio may not be less than 1.25 x. • During a Springing Covenant Period, as of the last day of any fiscal quarter (i) cash and cash equivalents of the Credit Parties must be at least $ 50.0 million and (ii) cash and cash equivalents of the Company and its subsidiaries must be at least $ 70.0 million. All obligations under the Credit Agreement (including under the Subline) are guaranteed by ADTRAN, Inc., and certain subsidiaries of ADTRAN, Inc. (“Full Facility Guarantors”). To secure such guarantees, ADTRAN, Inc. and the Full Facility Guarantors have granted security interests in favor of the Administrative Agent over substantially all of their tangible and intangible assets, and ADTRAN, Inc. has granted mortgages in favor of the Administrative Agent over certain owned real estate assets. Certain of Adtran Networks' subsidiaries ("Subline Guarantors") have provided a guarantee solely of the obligations in respect of the Subline. Furthermore, to secure such guarantees, the Subline Guarantors have granted security interests in favor of the Administrative Agent over substantially all of their tangible and intangible assets. Adtran Networks has also granted security interests in favor of the Administrative Agent over substantially all of its tangible and intangible assets, to secure solely its obligations under the Subline. Upon repayment in full and termination of the Subline, the guarantees by the Subline Guarantors and the liens granted by Adtran Networks and the Subline Guarantors to secure obligations under the Subline will be released. The Credit Agreement, as amended, contains customary affirmative and negative covenants, including incurrence covenants and certain other limitations on the ability of the Company and the Company’s subsidiaries to incur additional debt, guarantee other obligations, grant liens on assets, make investments, dispose of assets, make restricted payments, engage in mergers or consolidations, engage in transactions with affiliates, modify its organizational documents, and enter into certain restrictive agreements. The negative covenants are subject to various exceptions and carveouts. It also contains customary events of default, such as misrepresentation and a default in the performance or observance of any covenant (subject to customary cure periods and materiality thresholds). Upon the occurrence and during the continuance of an event of default, the Administrative Agent is entitled to take various actions, including the acceleration of all amounts due under the Credit Agreement.

Employee Benefit Plans

Employee Benefit Plans	9 Months Ended
	Sep. 30, 2024
Retirement Benefits [Abstract]
Employee Benefit Plans	12. EMPLOYEE BENEFIT PLANS Pension Benefit Plan We maintain a defined benefit pension plan covering employees in certain foreign countries. The Company's net non-current pension liability for all defined benefit pension plans totaled $ 12.1 million and $ 12.5 million as of September 30, 2024, and December 31, 2023, respectively, and the net current pension liability for all defined benefit pension plans totaled $ 0.1 million as of September 30, 2024, and December 31, 2023, which is included in accounts payable on the Condensed Consolidated Balance Sheets. The Company's defined benefit pension liability represents the projected benefit obligation, which is the actuarial present value of the vested benefits to which the employee is currently entitled based on the employee's expected date of retirement. The following table summarizes the components of net periodic pension cost related to the Company's defined benefit pension plans: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Service cost $ 340 $ 401 $ 1,013 $ 1,203 Interest cost 286 ( 33 ) 852 ( 99 ) Expected return on plan assets ( 360 ) 59 ( 1,074 ) 177 Amortization of actuarial losses 2 7 7 20 Net periodic pension cost $ 268 $ 434 $ 798 $ 1,301 The components of net periodic pension cost, other than the service cost component, are included in other (expense) income, net in the Condensed Consolidated Statements of Loss. Service cost is included in cost of revenue, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statements of Loss. The Company made contributions to the defined benefit pension plans totaling $ 3.0 million and $ 2.8 million during the nine months ended September 30, 2024 and 2023, respectively. Contributions to the defined benefit pension plans for the remainder of 2024 will be limited to benefit payments to retirees which are paid out of the operating cash flows of the Company and are expected to be approximately $ 1.0 million.

Equity

Equity	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Equity	13. EQUITY Accumulated Other Comprehensive Income The following tables present the changes in accumulated other comprehensive income, net of tax, by component: Three Months Ended September 30, 2024 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of June 30, 2024 $ ( 382 ) $ ( 2,573 ) $ 30,850 $ 385 $ 28,280 Other comprehensive (loss) income before ( 10 ) — 18,988 — 18,978 Amounts reclassified from accumulated other 10 109 — — 119 Net current period other comprehensive gain — 109 18,988 — 19,097 Balance as of September 30, 2024 $ ( 382 ) $ ( 2,464 ) $ 49,838 $ 385 $ 47,377 Three Months Ended September 30, 2023 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of June 30, 2023 $ ( 773 ) $ ( 958 ) $ 42,831 $ 385 $ 41,485 Other comprehensive income (loss) before 635 — ( 29,715 ) — ( 29,080 ) Amounts reclassified from accumulated other ( 244 ) ( 83 ) — — ( 327 ) Net current period other comprehensive income (loss) 391 ( 83 ) ( 29,715 ) — ( 29,407 ) Less: Comprehensive income attributable to non-controlling interest, net of tax — — — — — Balance as of September 30, 2023 $ ( 382 ) $ ( 1,041 ) $ 13,116 $ 385 $ 12,078 Nine Months Ended September 30, 2024 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of December 31, 2023 $ ( 382 ) $ ( 2,506 ) $ 49,968 $ 385 $ 47,465 Other comprehensive loss before ( 134 ) — ( 130 ) — ( 264 ) Amounts reclassified from accumulated other 134 42 — — 176 Net current period other comprehensive income (loss) — 42 ( 130 ) — ( 88 ) Balance as of September 30, 2024 $ ( 382 ) $ ( 2,464 ) $ 49,838 $ 385 $ 47,377 Nine Months Ended September 30, 2023 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of December 31, 2022 $ ( 836 ) $ ( 1,016 ) $ 27,593 $ 385 $ 26,126 Other comprehensive income (loss) before 733 — ( 14,095 ) — ( 13,362 ) Amounts reclassified from accumulated other ( 279 ) ( 25 ) — — ( 304 ) Net current period other comprehensive income (loss) 454 ( 25 ) ( 14,095 ) — ( 13,666 ) Less: Comprehensive income attributable to non-controlling — — 382 — 382 Balance as of September 30, 2023 $ ( 382 ) $ ( 1,041 ) $ 13,116 $ 385 $ 12,078 The following tables present the details of reclassifications out of accumulated other comprehensive income: Three Months Ended September 30, 2024 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized loss on sales of securities $ ( 13 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial loss ( 158 ) (1) Total reclassifications for the period, before tax ( 171 ) Tax expense 52 Total reclassifications for the period, net of tax $ ( 119 ) (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. Three Months Ended September 30, 2023 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized gain on sales of securities $ 321 Net investment gain (loss) Defined benefit plan adjustments – actuarial gain 120 (1) Total reclassifications for the period, before tax 441 Tax benefit ( 114 ) Total reclassifications for the period, net of tax $ 327 (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. Nine Months Ended September 30, 2024 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized loss on sales of securities $ ( 181 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial loss ( 61 ) (1) Total reclassifications for the period, before tax ( 242 ) Tax expense 66 Total reclassifications for the period, net of tax $ ( 176 ) (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. Nine Months Ended September 30, 2023 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized gain on sales of securities $ 367 Net investment gain (loss) Defined benefit plan adjustments – actuarial gain 36 (1) Total reclassifications for the period, before tax 403 Tax benefit ( 99 ) Total reclassifications for the period, net of tax $ 304 (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. The following table presents the tax effects related to the change in each component of other comprehensive (loss) income: Three Months Ended Three Months Ended September 30, 2024 September 30, 2023 (In thousands) Before-Tax Tax Net-of-Tax Before-Tax Tax Net-of-Tax Unrealized (loss) gain on available-for-sale $ ( 13 ) $ 3 $ ( 10 ) $ 836 $ ( 201 ) $ 635 Reclassification adjustment for amounts related to available-for-sale investments included in net gain (loss) 13 ( 3 ) 10 ( 321 ) 77 ( 244 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net gain (loss) 158 ( 49 ) 109 ( 120 ) 37 ( 83 ) Foreign currency translation adjustments 18,988 — 18,988 ( 29,715 ) — ( 29,715 ) Total Other Comprehensive Income (Loss) $ 19,146 $ ( 49 ) $ 19,097 $ ( 29,320 ) $ ( 87 ) $ ( 29,407 ) Nine Months Ended Nine Months Ended September 30, 2024 September 30, 2023 (In thousands) Before-Tax Tax Net-of-Tax Before-Tax Tax Net-of-Tax Unrealized (loss) gain on available-for-sale $ ( 181 ) $ 47 $ ( 134 ) $ 964 $ ( 231 ) $ 733 Reclassification adjustment for amounts related to available-for-sale investments included in net gain (loss) 181 ( 47 ) 134 ( 367 ) 88 ( 279 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net gain (loss) 61 ( 19 ) 42 ( 36 ) 11 ( 25 ) Foreign currency translation adjustments ( 130 ) — ( 130 ) ( 14,095 ) — ( 14,095 ) Total Other Comprehensive Loss $ ( 69 ) $ ( 19 ) $ ( 88 ) $ ( 13,534 ) $ ( 132 ) $ ( 13,666 )

Redeemable Non-controlling Inte

Redeemable Non-controlling Interest	9 Months Ended
	Sep. 30, 2024
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Redeemable Non-controlling Interest	14. REDEEMABLE NON-CONTROLLING INTEREST As of September 30, 2024 , the non-controlling Adtran Networks stockholders’ equity ownership percentage in Adtran Networks was approximately 33.0 %. The following table summarizes the redeemable non-controlling interest activity for the nine months ended September 30, 2024 and for the year ended December 31, 2023: Nine Months Ended For the Year Ended (In thousands) September 30, 2024 December 31, 2023 Balance at beginning of period $ 442,152 $ — Reclassification of non-controlling interests — 443,757 Redemption of redeemable non-controlling interest ( 20,376 ) ( 1,657 ) Net income attributable to redeemable non-controlling interests 7,417 10,092 (1) Annual recurring compensation earned ( 7,417 ) ( 10,092 ) (1) Adtran Networks stock option exercises — 52 Balance at end of period $ 421,776 $ 442,152 (1) (1) Following the third quarter of 2024, the Company identified errors primarily impacting the carrying values of the redeemable non-controlling interest, retained deficit, the net income attributable to the non-controlling interest and the net loss attributable to the Company and, as a consequence, of the loss per common share attributable to the Company. We have revised our previously issued Condensed Consolidated Financial Statements for the periods ended March 31, 2023, June 30, 2023, September 30, 2023, December 31, 2023, March 31, 2024 and June 30, 2024. See Note 1 for additional information. Annual recurring compensation payable on untendered outstanding shares under the DPLTA must be recognized as it is accrued. For the three and nine months ended September 30, 2024, we have accrued $ 2.4 million and $ 7.4 million, respectively, representing the portion of the annual recurring cash compensation to the non-controlling shareholders during such periods, which will be paid after the ordinary general shareholders' meeting of Adtran Networks in 2025. For the year ended December 31, 2023, w e paid $ 10.1 mi llion representing the portion of the annual recurring cash compensation to the non-controlling shareholders during such period. See Note 1 for additional information on RNCI and the annual dividend .

Loss Per Share

Loss Per Share	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Loss Per Share	15. LOSS PER SHARE The calculation of basic and diluted loss per share is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share amounts) 2024 2023 2024 2023 Numerator Net loss attributable to ADTRAN Holdings, Inc. $ ( 31,239 ) $ ( 78,210 ) $ ( 404,955 ) $ ( 156,697 ) Effect of redemption of RNCI 2,976 — 2,976 — Net loss attributable to ADTRAN Holdings, Inc. common shareholders $ ( 28,263 ) $ ( 78,210 ) $ ( 401,979 ) $ ( 156,697 ) Denominator Weighted average number of shares – basic 78,952 78,389 78,873 78,378 Effect of dilutive securities Stock options — — — — PSUs, RSUs and restricted stock — — — — Weighted average number of shares – diluted 78,952 78,389 78,873 78,378 Loss per share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.36 ) $ ( 1.00 ) $ ( 5.10 ) $ ( 2.00 ) Loss per share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.36 ) $ ( 1.00 ) $ ( 5.10 ) $ ( 2.00 ) For the three months ended September 30, 2024 and 2023 , 0.9 million and 0.5 million shares, respectively, and for the nine months ended September 30, 2024 and 2023 , 1.1 million and 0.4 million, 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 September 30, 2024 and 2023 , 4.0 million and 2.6 million stock options, respectively, and for the nine months ended September 30, 2024 and 2023 , 4.2 million and 1.4 million stock options, respectively, were outstanding but were not included in the computation of diluted earnings per share. Thes e 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	9 Months Ended
	Sep. 30, 2024
Segment Reporting [Abstract]
Segment Information	16. SEGMENT INFORMATION The chief operating decision maker regularly reviews the Company’s financial performance based on two reportable segments: (1) Network Solutions and (2) Services & Support. The Network Solutions segment includes hardware and software products that enable a digital future which support the Company's Subscriber, Access & Aggregation, and Optical Networking Solutions. The Company's cloud-managed Wi-Fi gateways, virtualization software, and switches provide a mix of wired and wireless connectivity at the customer premises. In addition, its Carrier Ethernet products support a variety of applications at the network edge ranging from mobile backhaul to connecting enterprise customers (“Subscriber Solutions"). The Company's portfolio includes products for multi-gigabit service delivery over fiber or alternative media to homes and businesses. The Services & Support segment offers a comprehensive portfolio of network design, implementation, maintenance and cloud-hosted services supporting its Subscriber, Access & Aggregation, and Optical Networking Solutions. These services assist operators in the deployment of multi-vendor networks while reducing their cost to maintain these networks. The cloud-hosted services include a suite of SaaS applications under the Company's Mosaic One platform that manages end-to-end network and service optimization for both fiber access infrastructure and mesh Wi-Fi connectivity. The Company backs these services with a global support organization that offers on-site and off-site support services with varying SLAs. The performance of these segments is evaluated based on revenue, gross profit and gross margin; therefore, selling, general and administrative expenses, research and development expenses, interest and dividend income, interest expense, net investment gain, other income (expense), net and income tax benefit are reported on a consolidated basis only. There is no inter-segment revenue. Asset information by reportable segment is not produced and, therefore, is not reported. The following tables present information about the revenue and gross profit of the Company's reportable segments: Three Months Ended September 30, 2024 September 30, 2023 (In thousands) Revenue Gross Profit Revenue Gross Profit Network Solutions $ 181,488 $ 55,713 $ 228,564 $ 47,277 Services & Support 46,216 29,538 43,767 26,960 Total $ 227,704 $ 85,251 $ 272,331 $ 74,237 Nine Months Ended September 30, 2024 September 30, 2023 (In thousands) Revenue Gross Profit Revenue Gross Profit Network Solutions $ 541,955 $ 156,472 $ 793,984 $ 176,607 Services & Support 137,913 82,609 129,637 77,991 Total $ 679,868 $ 239,081 $ 923,621 $ 254,598 For each of the three months ended September 30, 2024 and 2023 , $ 2.9 million and $ 1.5 million, respectively, of depreciation expense was included in gross profit for our Network Solutions segment. For the nine months ended September 30, 2024 and 2023 , $ 7.4 million and $ 4.5 million, respectively, of depreciation expense was included in gross profit for our Network Solutions segment. For the three months ended September 30, 2024 and 2023 , $ 0.1 million and $ 2 thousand, respectively, of depreciation expense was included in gross profit for our Services & Support segment. For the nine months ended September 30, 2024 and 2023 , $ 0.2 million and $ 7 thousand, respectively, of depreciation expense was included in gross profit for our Services & Support segment. Revenue by Geographic Area The following table presents revenue information by geographic area: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 United States $ 102,527 $ 111,494 $ 293,420 $ 375,254 United Kingdom 49,366 60,347 145,666 212,171 Germany 27,270 41,242 91,553 150,710 Other international 48,541 59,248 149,229 185,486 Total $ 227,704 $ 272,331 $ 679,868 $ 923,621

Liability for Warranty Returns

Liability for Warranty Returns	9 Months Ended
	Sep. 30, 2024
Product Warranties Disclosures [Abstract]
Liability for Warranty Returns	17. LIABILITY FOR WARRANTY RETURNS The Company's products generally include warranties of 90 days to five years for product defects. The Company accrues for warranty returns at the time of product shipment based on its historical return rate and estimate of the cost to repair or replace the defective products. The Company engages in extensive product quality programs and processes, including actively monitoring and evaluating the quality of its component suppliers. The increasing complexity of the Company's 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 the Company's actual experience relative to these factors be worse than its estimates, the Company will record additional warranty expense. The liability for warranty obligations totaled $ 5.6 million and $ 6.4 million as of September 30, 2024 and December 31, 2023 , respectively, and is included in accrued expenses and other liabilities in the Condensed Consolidated Balance Sheets. The warranty expense and write-off activity for the three and nine months ended September 30, 2024 and 2023 are summarized as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Balance at beginning of period $ 6,024 $ 6,831 $ 6,445 $ 7,196 Plus: Amounts charged to cost and expenses 395 752 1,779 2,289 Plus: Foreign currency translation adjustments 84 ( 73 ) 21 ( 33 ) Less: Deductions ( 854 ) ( 943 ) ( 2,596 ) ( 2,885 ) Balance at end of period $ 5,649 $ 6,567 $ 5,649 $ 6,567

Commitments and Contingencies

Commitments and Contingencies	9 Months Ended
	Sep. 30, 2024
Commitments and Contingencies Disclosure [Abstract]
Commitments and Contingencies	18. COMMITMENTS AND CONTINGENCIES Legal Matters From time to time, the Company is 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 a 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. The Company records an accrual for any Legal Matters that arise whenever it considers that it is probable that it is exposed to a loss contingency and the amount of the loss contingency can be reasonably estimated. Although the ultimate disposition of asserted claims cannot be predicted with certainty, it is our belief that the outcome of any such claims, either individually or on a combined basis, will not have a material adverse effect on our consolidated financial position. DPLTA Exit and Recurring Compensation Costs Pursuant to the terms of the DPLTA, each Adtran Networks shareholder (other than the Company) has received an offer to elect either (1) to remain an Adtran Networks shareholder and receive from us an Annual Recurring Compensation payment, or (2) to receive Exit Compensation plus guaranteed interest. The guaranteed interest under the Exit Compensation is calculated from the effective date of the DPLTA to the date the shares are tendered, less any Annual Recurring Compensation paid. The guaranteed interest rate is 5.0 % plus a variable component (according to the German Civil Code) that was 3.37 % as of September 30, 2024. Assuming all the minority holders of currently outstanding Adtran Networks shares were to elect the second option, we would be obligated to make aggregate Exit Compensation payments, including guaranteed interest, of approximately € 326.9 million or approximately $ 364.1 million, based on an exchange rate as of September 30, 2024, and reflecting interest accrued through September 30, 2024 , during the pendency of the appraisal proceedings discussed below. Shareholders electing the first option of Annual Recurring Compensation may later elect the second option. The opportunity for outside Adtran Networks shareholders to tender Adtran Networks shares in exchange for Exit Compensation had been scheduled to expire on March 16, 2023 . However, due to the appraisal proceedings that have been initiated in accordance with applicable German law, this time period for tendering shares has been extended pursuant to the German Stock Corporation Act (Aktiengesetz) and will end two months after the date on which a final decision in such appraisal proceedings has been published in the Federal Gazette (Bundesanzeiger). Our obligation to pay Annual Recurring Compensation under the DPLTA is a continuing payment obligation, which will amount to approximately € 8.9 million (or $ 10.0 million based on the current exchange rate) per year assuming none of the minority Adtran Networks shareholders were to elect Exit Compensation. The foregoing amounts do n ot reflect any potential increase in payment obligations that we may have depending on the outcome of ongoing appraisal proceedings in Germany. The Annual Recurring Compensation is due on the third banking day following the ordinary general shareholders’ meeting of Adtran Networks for the respective preceding fiscal year (but in any event within eight months following expiration of the fiscal year). With respect to the 2023 fiscal year, Adtran Networks’ ordinary general shareholders’ meeting occurred on June 28, 2024 and, therefore, the Annual Recurring Compensation was paid on July 3, 2024. During the three months ended September 30, 2024 and 2023, we accrued $ 2.4 million and $ 2.6 million, r espectively, in Annual Recurring Compensation. During the nine months ended September 30, 2024 and 2023, we accrued $ 7.4 million and $ 7.6 million, r espectively, in Annual Recurring Compensation, which was reflected as an increase to retained deficit. For the three and nine months ended September 30, 2024, approximately 830 thousand shares and 831 thousand shares, respectively, of Adtran Networks stock were tendered to the Company. This resulted in total Exit Compensation payments of approximately € 15.7 million, or approximately $ 17.4 million , based on an exchange rate as of September 30, 2024, being paid to Adtran Networks shareholders. For the three and nine months ended September 30, 2023, less than 1 thousand shares and 64 thousand shares, respectively, of Adtran Networks stock were tendered to the Company. This resulted in Exit Compensation payments of approximately € 8 thousand and € 1.1 million, respectively, or approximately $ 9 thousand and $ 1.2 million, respectively, based on an exchange rate as of September 30, 2023, being paid to Adtran Networks shareholders. Performance Bonds Certain contracts, customers and jurisdictions in which we do business require us to provide various guarantees of performance such as bid bonds, performance bonds and customs bonds. As of September 30, 2024, and December 31, 2023, we had commitments related to these bonds totaling $ 14.6 million and $ 10.8 million, respectively, which expire at various dates through April 2031 . 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. Purchase Obligations The Company purchases components from a variety of suppliers and uses contract manufacturers to provide manufacturing services for our products. Our inventory purchase obligations are for product manufacturing requirements, as well as for commitments to suppliers to secure manufacturing capacity. Certain of our inventory purchase obligations with contract manufacturers and suppliers relate to arrangements to secure supply and pricing for certain product components for multi-year periods. As of September 30, 2024, purchase obligations totaled $ 261.8 mi llion.

Restructuring

Restructuring	9 Months Ended
	Sep. 30, 2024
Restructuring and Related Activities [Abstract]
Restructuring	19. RESTRUCTURING During the fourth quarter of 2022, the Company initiated a restructuring program designed to optimize the assets, business processes, and information technology systems of the Company in relation to the Business Combination with Adtran Networks. The restructuring program is expected to maximize cost synergies by realizing operation scale, combining sales channels, streamlining corporate and general and administrative functions, including human capital resources and combining sourcing and production costs. This restructuring program is expected to be completed in late 2024 and includes expenses specifically associated with achieving run-rate synergies, as well as Business Efficiency Program expenses described below. On November 6, 2023, due to the uncertainty around the current macroeconomic environment and its impact on customer spending levels, the Company’s management decided to implement a business efficiency program (“Business Efficiency Program”) targeting the reduction of ongoing operating expenses and focusing on capital efficiency inclusive of certain salary reductions, an early retirement program, a site consolidation plan to include lease impairments and the partial sale of owned real estate (including the potential sale of portions of our headquarters), inventory write downs from product discontinuances, and the suspension of the quarterly dividend. The Business Efficiency Program expands upon other recently implemented restructuring efforts and synergy costs following the Business Combination. For instance, on August 17, 2023, the Company’s management determined to discontinue its copper-based Digital Subscriber Line broadband access technology products and its fixed wireless access products in its Network Solutions segment. Furthermore, on September 29, 2023, the Company’s management decided to exit the "IoT" gateway market (indoor and outdoor), a subset of the broader IoT market (together with the other product discontinuations, the “Discontinuations”). On October 25, 2023, all employees were informed of certain personnel measures, which included the reduction of salary for select management, a reduction of approximately 5 % of the workforce, an early retirement program and a hiring freeze. Additionally, on April 11, 2024, Management determined to close a facility in Greifswald, Germany. The closure of the facility is expected to be completed by December 31, 2024. During the three and nine months ended September 30, 2024 , we recognized $ 5.9 million and $ 40.6 million of costs related to the Business Efficiency Program, respectively. The costs recognized during the nine months ended September 30, 2024 , included total other renegotiated charges and inventory write-down of $ 8.6 million as a result of a strategy shift which included discontinuance of certain items in connection with the Business Efficiency Program, of which, $ 4.1 million relates to inventory write-downs and $ 4.5 million relates to other charges, and are included in cost of revenue in the Condensed Consolidated Statements of Loss. Since the inception of the Business Efficiency Program, we recognized $ 65.6 million of costs. We expect costs in the fourth quarter 2024 relating to the Business Efficiency Program to range between $ 9.6 million and $ 13.8 million. Management expects these planned costs to include severance costs to be approximately $ 6.2 million in connection with reductions in workforce and site consolidation transaction expenses (primarily brokers fees and Greifswald exit costs) ranging from $ 3.4 million to $ 7.6 million. The broker fees related to our site consolidation expenses will be netted against proceeds upon the sale of the building(s). Future cash payments include: severance costs and outplacement fees that are anticipated to be $ 23.1 million, and payments relating to the site consolidation transaction expenses that are anticipated to be in the range of $ 3.4 million to $ 7.6 million. We do not anticipate any remaining payments related to the inventory strategy shift. We may also incur other charges or cash expenditures not currently contemplated due to events that may occur as a result of, or associated with, the Business Efficiency Program, including potential impairment charges related to the discontinuance of additional product lines, regulatory requirements related to personnel measures, and site closures.  However, we are not able to estimate the amount or range of amounts of such potential incremental charges as of the date of this filing. If required, we will amend this disclosure at such time as management is able in good faith to estimate the amount, or range of amounts, of these charges. For the three and nine months ended September 30, 2023 , we recognized $ 24.9 million and $ 33.2 million of restructuring costs relating to the Business Combination under the multi-year integration program and synergy realization that are included in cost of revenue, selling, general and administrative expenses and research and development expenses in the Condensed Consolidated Statement of Loss, respectively. This included the write down of inventory of $ 21.0 million due to a restructuring discontinuation of certain product lines within our Network Solutions segment during the three and nine months ended September 30, 2023. See Note 6, Inventory, for additional information regarding the write down of inventory. A reconciliation of the beginning and ending restructuring liabilities, which is included in accrued wages and benefits and accounts payable in the Condensed Consolidated Balance Sheets as of September 30, 2024, and December 31, 2023, is as follows: Three Months Ended Nine Months Ended (In thousands) September 30, 2024 September 30, 2024 Balance at beginning of period $ 18,657 $ 8,309 Plus: Amounts charged to cost and expense 5,936 36,441 Less: Amounts paid ( 7,770 ) ( 27,927 ) Balance as of September 30, 2024 $ 16,823 $ 16,823 For the Year Ended (In thousands) December 31, 2023 Balance as of December 31, 2022 $ 159 Plus: Amounts charged to cost and expense 22,241 Less: Amounts paid ( 14,091 ) Balance as of December 31, 2023 $ 8,309 Restructuring expenses included in the Condensed Consolidated Statements of Loss are for the three and nine months ended September 30, 2024 and 2023: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Network Solutions - Cost of revenue $ 517 $ 611 $ 3,359 $ 669 Network Solutions - other (credits), charges ( 328 ) 21,043 $ 8,597 21,043 Services & Support - Cost of revenue ( 182 ) ( 24 ) 2,086 ( 6 ) Cost of revenue $ 7 $ 21,630 $ 14,042 $ 21,706 Selling, general and administrative expenses 2,681 3,387 7,980 6,960 Research and development expenses 3,248 ( 144 ) 18,554 4,512 Total restructuring expenses $ 5,936 $ 24,873 $ 40,576 $ 33,178 The following table represents the components of restructuring expenses by geographic area for the three and nine months ended September 30, 2024 and 2023: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 United States $ 1,208 $ 22,598 $ 17,495 $ 25,217 International 4,728 2,275 23,081 7,961 Total restructuring expenses $ 5,936 $ 24,873 $ 40,576 $ 33,178

Summary of Significant Accoun_2

Summary of Significant Accounting Policies (Policies)	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Basis of Presentation	Basis of Presentation The accompanying unaudited Condensed Consolidated Financial Statements of ADTRAN Holdings, Inc. and its subsidiaries have been prepared pursuant to the rules and regulations of the SEC applicable to interim financial information presented in Quarterly Reports on Form 10-Q. Accordingly, certain information and notes required by generally accepted accounting principles in the United States of America (“U.S. GAAP”) for complete financial statements are not included herein. The December 31, 2023, Condensed Consolidated Balance Sheet is derived from audited financial statements but does not include all disclosures required by U.S. GAAP for annual financial statements. 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 Holdings, Inc. Annual Report on Form 10-K for the year ended December 31, 2023 , filed with the SEC on March 15, 2024.
Revision of Previously Issued Condensed Consolidated Financial Statements	Revision of Previously Issued Condensed Consolidated Financial Statements Following the third quarter of 2024, the Company identified errors primarily impacting the carrying values of the redeemable non-controlling interest, retained deficit, the net income attributable to the non-controlling interest and the net loss attributable to the Company and, as a consequence, of the loss per common share attributable to the Company. The Company has evaluated the errors and determined that the related impacts were not material to the previously issued consolidated financial statements for any prior period. A summary of the corrections to the Company's Condensed Consolidated Financial Statements for the periods ended March 31, 2023, June 30, 2023, September 30, 2023, December 31, 2023, March 31, 2024 and June 30, 2024, are as follows: (a) Pursuant to the terms of the DPLTA, each Adtran Networks shareholder (other than the Company) is entitled to receive from us an Annual Recurring Compensation payment of € 0.52 per share. The Company erroneously accrued this liability every quarter at € 0.59 per share, overstating the associated accrual, the net income attributable to non-controlling interest and the net loss attributable to ADTRAN Holdings, Inc. for fiscal periods beginning with the quarter ended March 31, 2023 through the quarter ended June 30, 2024. (b) For the periods beginning with the quarter ended March 31, 2023 through the quarter ended June 30, 2024 the Company remeasured the redeemable non-controlling interest each quarter-end at the current exchange rate of Euros to U.S. Dollar. The Company treated the redeemable non-controlling interest as a monetary mezzanine equity instrument but should have treated it as a non-monetary mezzanine equity instrument not subject to remeasurement. We have revised our previously issued Condensed Consolidated Financial Statements for the periods ended March 31, 2023, June 30, 2023, September 30, 2023, December 31, 2023, March 31, 2024 and June 30, 2024. Additionally, the Company will revise its previously issued 2023 interim financial statements and 2023 annual financial statements in connection with the future filings of the Form 10-K for the year ended December 31, 2024, and interim reporting on Form 10-Q for the periods ended March 31, 2025 and June 30, 2025. The following tables reflect the impact of the revision to the specific line items presented in the Company's previously reported Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Loss, and Condensed Consolidated Statements of Comprehensive Loss for the for fiscal periods beginning with the quarter ended March 31, 2023 through the quarter ended June 30, 2024. March 31, 2023 (In thousands) As Previously Reported Revision As Revised Other non-current liabilities $ 15,986 $ ( 346 ) (a) $ 15,640 Total Liabilities $ 675,765 $ (346 ) $ 675,419 Redeemable Non-Controlling Interest $ 442,668 $ ( 430 ) (b) $ 442,238 Accumulated Other Comprehensive Income $ 34,526 $ 1 (a) $ 34,527 Retained Earnings $ 8,006 $ 775 (a)(b) $ 8,781 Total Equity $ 820,162 $ 776 $ 820,938 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,938,595 $ — $ 1,938,595 For the Three Months Ended March 31, 2023 (In thousands) As Previously Reported Revision As Revised Less: Net Loss attributable to non-controlling interest $ ( 370 ) $ ( 345 ) (a) $ ( 715 ) Net Loss attributable to ADTRAN Holdings, Inc. $ ( 40,083 ) $ 345 (a) $ ( 39,738 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.51 ) $ — $ ( 0.51 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.51 ) $ — $ ( 0.51 ) Foreign currency translation gain $ 8,678 $ 1 (a) $ 8,679 Other Comprehensive Income, net of tax $ 8,782 $ 1 $ 8,783 Comprehensive Loss, net of tax $ ( 31,671 ) $ 1 $ ( 31,670 ) Less: Comprehensive Income (Loss) attributable to non-controlling interest, net of tax $ 12 $ ( 345 ) (a) $ ( 333 ) Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 31,683 ) $ 346 (a) $ ( 31,337 ) June 30, 2023 (In thousands) As Previously Reported Revision As Revised Other non-current liabilities $ 16,401 $ ( 695 ) (a) $ 15,706 Total Liabilities $ 665,006 $ (695 ) $ 664,311 Redeemable Non-Controlling Interest $ 445,462 $ ( 3,244 ) (b) $ 442,218 Accumulated Other Comprehensive Income $ 41,483 $ 2 (a) $ 41,485 Retained Deficit $ ( 41,010 ) $ 3,937 (a)(b) $ ( 37,073 ) Total Equity $ 782,470 $ 3,939 $ 786,409 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,882,938 $ — $ 1,882,938 For the Three Months Ended June 30, 2023 For the Six Months Ended June 30, 2023 (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,882 $ ( 348 ) (a) $ 2,534 $ 2,512 $ ( 693 ) (a) $ 1,819 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 39,097 ) $ 348 (a) $ ( 38,749 ) $ ( 79,180 ) $ 693 (a) $ ( 78,487 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.50 ) $ — $ ( 0.50 ) $ ( 1.01 ) $ 0.01 (a) $ ( 1.00 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.50 ) $ — $ ( 0.50 ) $ ( 1.01 ) $ 0.01 (a) $ ( 1.00 ) Foreign currency translation gain $ 6,940 $ 1 (a) $ 6,941 $ 15,618 $ 2 (a) $ 15,620 Other Comprehensive Income, net of tax $ 6,957 $ 1 $ 6,958 $ 15,739 $ 2 $ 15,741 Comprehensive Loss, net of tax $ ( 29,258 ) $ 1 $ ( 29,257 ) $ ( 60,929 ) $ 2 $ ( 60,927 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,882 $ ( 348 ) (a) $ 2,534 $ 2,894 $ ( 693 ) (a) $ 2,201 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 32,140 ) $ 349 (a) $ ( 31,791 ) $ ( 63,823 ) $ 695 (a) $ ( 63,128 ) September 30, 2023 (In thousands) As Previously Reported Revision As Revised Other non-current liabilities $ 17,408 $ ( 1,049 ) (a) $ 16,359 Total Liabilities $ 625,355 $ (1,049 ) $ 624,306 Redeemable Non-Controlling Interest $ 431,921 $ 10,291 (b) $ 442,212 Accumulated Other Comprehensive Income $ 12,075 $ 3 (a) $ 12,078 Retained Deficit $ ( 113,289 ) $ ( 9,245 ) (a)(b) $ ( 122,534 ) Total Equity $ 684,893 $ ( 9,242 ) $ 675,651 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,742,169 $ — $ 1,742,169 For the Three Months Ended September 30, 2023 For the Nine Months Ended September 30, 2023 (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,914 $ ( 353 ) (a) $ 2,561 $ 5,426 $ ( 1,046 ) (a) $ 4,380 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 78,563 ) $ 353 (a) $ ( 78,210 ) $ ( 157,743 ) $ 1,046 (a) $ ( 156,697 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 1.00 ) $ — $ ( 1.00 ) $ ( 2.01 ) $ 0.01 (a) $ ( 2.00 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 1.00 ) $ — $ ( 1.00 ) $ ( 2.01 ) $ 0.01 (a) $ ( 2.00 ) Foreign currency translation loss $ ( 29,716 ) $ 1 (a) $ ( 29,715 ) $ ( 14,098 ) $ 3 (a) $ ( 14,095 ) Other Comprehensive Loss, net of tax $ ( 29,408 ) $ 1 $ ( 29,407 ) $ ( 13,669 ) $ 3 $ ( 13,666 ) Comprehensive Loss, net of tax $ ( 105,057 ) $ 1 $ ( 105,056 ) $ ( 165,986 ) $ 3 $ ( 165,983 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,914 $ ( 353 ) (a) $ 2,561 $ 5,808 $ ( 1,046 ) (a) $ 4,762 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 107,971 ) $ 354 (a) $ ( 107,617 ) $ ( 171,794 ) $ 1,049 (a) $ ( 170,745 ) March 31, 2024 (In thousands) As Previously Reported Revision As Revised Accrued Expenses and Other Liabilities $ 36,404 $ ( 1,403 ) (a) $ 35,001 Total Current Liabilities $ 282,746 $ (1,403 ) $ 281,343 Other non-current liabilities $ 35,375 $ (350 ) (a) $ 35,025 Total Liabilities $ 620,488 $ (1,753 ) $ 618,735 Redeemable Non-Controlling Interest $ 441,635 $ 511 (b) $ 442,146 Accumulated Other Comprehensive Income $ 29,656 $ 5 (a) $ 29,661 Retained Deficit $ ( 558,363 ) $ 1,237 (a)(b) $ ( 557,126 ) Total Equity $ 265,783 $ 1,242 $ 267,025 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,327,906 $ — $ 1,327,906 For the Three Months Ended March 31, 2024 (In thousands) As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,880 $ ( 349 ) (a) $ 2,531 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 324,550 ) $ 349 (a) $ ( 324,201 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 4.12 ) $ — $ ( 4.12 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 4.12 ) $ — $ ( 4.12 ) Foreign currency translation loss $ ( 17,745 ) $ 1 (a) $ ( 17,744 ) Other Comprehensive Loss, net of tax $ ( 17,805 ) $ 1 $ ( 17,804 ) Comprehensive Loss, net of tax $ ( 339,475 ) $ 1 $ ( 339,474 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,880 $ ( 349 ) (a) $ 2,531 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 342,355 ) $ 350 (a) $ ( 342,005 ) June 30, 2024 (In thousands) As Previously Reported Revision As Revised Accrued Expenses and Other Liabilities $ 36,307 $ ( 1,403 ) (a) $ 34,904 Total Current Liabilities $ 289,712 $ (1,403 ) $ 288,309 Other non-current liabilities $ 34,445 $ (701 ) (a) $ 33,744 Total Liabilities $ 630,810 $ (2,104 ) $ 628,706 Redeemable Non-Controlling Interest $ 439,743 $ 2,379 (b) $ 442,122 Accumulated Other Comprehensive Income $ 28,274 $ 6 (a) $ 28,280 Retained Deficit $ ( 606,375 ) $ ( 281 ) (a)(b) $ ( 606,656 ) Total Equity $ 220,229 $ ( 275 ) $ 219,954 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,290,782 $ — $ 1,290,782 For the Three Months Ended June 30, 2024 For the Six Months Ended June 30, 2024 (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,854 $ ( 350 ) (a) $ 2,504 $ 5,734 $ ( 699 ) (a) $ 5,035 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 49,865 ) $ 350 (a) $ ( 49,515 ) $ ( 374,415 ) $ 699 (a) $ ( 373,716 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.63 ) $ — $ ( 0.63 ) $ ( 4.75 ) $ 0.01 (a) $ ( 4.74 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.63 ) $ — $ ( 0.63 ) $ ( 4.75 ) $ 0.01 (a) $ ( 4.74 ) Foreign currency translation loss $ ( 1,375 ) $ 1 (a) $ ( 1,374 ) $ ( 19,120 ) $ 2 (a) $ ( 19,118 ) Other Comprehensive Loss, net of tax $ ( 1,382 ) $ 1 $ ( 1,381 ) $ ( 19,187 ) $ 2 $ ( 19,185 ) Comprehensive Loss, net of tax $ ( 48,393 ) $ 1 $ ( 48,392 ) $ ( 387,868 ) $ 2 $ ( 387,866 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,854 $ ( 350 ) (a) $ 2,504 $ 5,734 $ ( 699 ) (a) $ 5,035 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 51,247 ) $ 351 (a) $ ( 50,896 ) $ ( 393,602 ) $ 701 (a) $ ( 392,901 ) The following tables reflect the impact of the revisions to the specific line items presented in the Company’s previously reported Consolidated Balance Sheet as of December 31, 2023, the Consolidated Statement of Loss and the Consolidated Statement of Comprehensive Loss for the year ended December 31, 2023. December 31, 2023 (In thousands) As Previously Reported Revision As Revised Accrued Expenses and Other Liabilities $ 37,607 $ ( 1,403 ) (a) $ 36,204 Total Current Liabilities $ 279,511 $ (1,403 ) $ 278,108 Total Liabilities $ 636,934 $ (1,403 ) $ 635,531 Redeemable Non-Controlling Interest $ 451,756 $ ( 9,604 ) (b) $ 442,152 Accumulated Other Comprehensive Income $ 47,461 $ 4 (a) $ 47,465 Retained Deficit $ ( 243,908 ) $ 11,003 (a)(b) $ ( 232,905 ) Total Equity $ 593,822 $ 11,007 $ 604,829 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,682,512 $ — $ 1,682,512 For the Year Ended December 31, 2023 (In thousands) As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 8,345 $ ( 1,399 ) (a) $ 6,946 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 267,688 ) $ 1,399 (a) $ ( 266,289 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 3.41 ) $ 0.02 (a) $ ( 3.39 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 3.41 ) $ 0.02 (a) $ ( 3.39 ) Foreign currency translation gain $ 22,753 $ 4 (a) $ 22,757 Other Comprehensive Income, net of tax $ 21,717 $ 4 $ 21,721 Comprehensive Loss, net of tax $ ( 237,626 ) $ 4 $ ( 237,622 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 8,727 $ ( 1,399 ) (a) $ 7,328 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 246,353 ) $ 1,403 (a) $ ( 244,950 ) The following tables reflect the impact of the revision to the specific line items presented in the Company's previously reported Condensed Consolidated Statements of Changes in Stockholders Equity as of September 30, 2023 and 2024: Retained Earnings (Deficit) Accumulated Other Comprehensive Income (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Annual recurring compensation earned $ ( 2,809 ) $ 345 (a) $ ( 2,464 ) $ - $ - $ - Other comprehensive income, net of tax $ - $ - $ - $ 8,400 $ 1 (a) $ 8,401 Foreign currency remeasurement of redeemable non-controlling interest $ ( 430 ) $ 430 (b) $ - $ - $ - $ - Balance as of March 31, 2023 $ 8,006 $ 775 $ 8,781 $ 34,526 $ 1 $ 34,527 Annual recurring compensation earned $ ( 2,882 ) $ 348 (a) $ ( 2,534 ) $ - $ - $ - Other comprehensive income, net of tax $ - $ - $ - $ 6,957 $ 1 (a) $ 6,958 Foreign currency remeasurement of redeemable non-controlling interest $ ( 2,814 ) $ 2,814 (b) $ - $ - $ - $ - Balance as of June 30, 2023 $ ( 41,010 ) $ 3,937 $ ( 37,073 ) $ 41,483 $ 2 $ 41,485 Annual recurring compensation earned $ ( 2,914 ) $ 353 (a) $ ( 2,561 ) $ - $ - $ - Other comprehensive loss, net of tax $ - $ - $ - $ ( 29,408 ) $ 1 (a) $ ( 29,407 ) Foreign currency remeasurement of redeemable non-controlling interest $ 13,535 $ ( 13,535 ) (b) $ - $ - $ - $ - Balance as of September 30, 2023 $ ( 113,289 ) $ ( 9,245 ) $ ( 122,534 ) $ 12,075 $ 3 $ 12,078 Retained Deficit Accumulated Other Comprehensive Income (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Balance as of December 31, 2023 $ ( 243,908 ) $ 11,003 (a) $ ( 232,905 ) $ 47,461 $ 4 (a) $ 47,465 Annual recurring compensation earned $ ( 2,880 ) $ 349 (a) $ ( 2,531 ) $ - $ - $ - Other comprehensive loss, net of tax $ - $ - $ - $ ( 17,805 ) $ 1 (a) $ ( 17,804 ) Foreign currency remeasurement of redeemable non-controlling interest $ 10,115 $ ( 10,115 ) (b) $ - $ - $ - $ - Balance as of March 31, 2024 $ ( 558,363 ) $ 1,237 $ ( 557,126 ) $ 29,656 $ 5 $ 29,661 Annual recurring compensation earned $ ( 2,854 ) $ 350 (a) $ ( 2,504 ) $ - $ - Other comprehensive loss, net of tax $ - $ - $ - $ ( 1,382 ) $ 1 (a) $ ( 1,381 ) Foreign currency remeasurement of redeemable non-controlling interest $ 1,868 $ ( 1,868 ) (b) $ - $ - $ - $ - Balance as of June 30, 2024 $ ( 606,375 ) $ ( 281 ) $ ( 606,656 ) $ 28,274 $ 6 $ 28,280 The following tables reflect the impact of the revision to the specific line items presented in the Company's previously reported Consolidated Statement of Changes in Stockholders as of December 31, 2023: Retained Earnings (Deficit) Accumulated Other Comprehensive Income (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Annual recurring compensation earned $ ( 11,524 ) $ 1,399 (a) $ ( 10,125 ) $ - $ - $ - Other comprehensive income, net of tax $ - $ - $ - $ 21,335 $ 4 (a) $ 21,339 Foreign currency remeasurement of redeemable non-controlling interest $ ( 9,604 ) $ 9,604 (b) $ - $ - $ - $ - Balance as of December 31, 2023 $ ( 243,908 ) $ 11,003 $ ( 232,905 ) $ 47,461 $ 4 $ 47,465
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 allowance for credit losses on accounts receivable and contract assets, 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 revenue 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, estimates of intangible assets upon measurement, estimated pension liability and fair value of investments and estimated contingent liabilities. 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 ongoing inflationary pressures, continued elevated interest rates, instability in the financial services industry, currency fluctuations and political tensions as of September 30, 2024, and through the date of this report. These conditions could result in further impacts to the Company's consolidated financial statements in future reporting periods. 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 as sets, revenue recognition and costs of revenue.
Accounts Receivable Factoring	Accounts Receivable Factoring Receivables Purchase Agreement On July 1, 2024, the Company entered into a receivables purchase agreement (the “Factoring Agreement”) with a third-party financial institution (the “Factor”), which accelerates receivable collection and helps to better manage cash flow. These transactions are accounted for in accordance with ASC Topic 860 and result in a reduction in accounts receivable because the Factoring Agreement transfers effective control over, and risk related to the receivables to the buyers. Trade accounts receivables balances sold are removed from the Condensed Consolidated Balance Sheets and cash received is reflected as cash flows provided by (used in) operating activities in the Condensed Consolidated Statements of Cash Flow. Factoring related interest expense is recorded to interest expense on the Condensed Consolidated Statements of Loss. On each sale date, the Factor retains from the sale price a default reserve, up to a required balance, which is held by the Factor in a reserve account and pledged to the Company. The Factor is entitled to withdraw from the reserve account the sale price of a defaulted receivable. The balance in the reserve account is included in other assets on the Condensed Consolidated Balance Sheets. Previous Receivables Purchase Agreement On December 19, 2023, the Company entered into a receivables purchase agreement (the “Prior Factoring Agreement”) with a third-party financial institution and was terminated on July 1, 2024. The Prior Factoring Agreement qualified for treatment as a secured borrowing with a pledge of collateral under Accounting Standards Codification ("ASC") Topic 810, Consolidations, as the Company was considered the primary beneficiary in a variable interest entity created to hold the factored receivables and the Company retained a residual claim on reserves related to the factored receivables . Within the Condensed Consolidated Balance Sheets, the receivables factored were carried in accounts receivable, less allowance for credit losses, and the secured borrowings were carried as a current liability within accounts payable. The proceeds and repayments of secured borrowings were reflected as cash flows (used in) provided by financing activities within the Condensed Consolidated Statements of Cash Flows, and program fees were recorded as interest expense in the Consolidated Statements of Loss. The short-term liability classification of the secured borrowings was based on the estimated timing of the collection of the accounts receivable which were expected to be received within 12 months. See Note 2 for additional information.
Redeemable Non-Controlling Interest	Redeemable Non-Controlling Interest As of September 30, 2024 and December 31, 2023, the non-controlling Adtran Networks stockholders’ equity ownership percentage in Adtran Networks was approximatel y 33.0 % and 34.6 %, respectively. As a result of the effectiveness of the DPLTA on January 16, 2023, the Adtran Networks shares, representing the equity interest in Adtran Networks held by holders other than the Company, can be tendered at any time and are, therefore, redeemable and must be classified outside stockholders’ equity. Therefore, the permanent equity noncontrolling interest balance was reclassified to redeemable non-controlling interest on January 16, 2023, and was remeasured to fair value based on the trading market price of the Adtran Networks shares. Subsequently, the carrying value of the RNCI is adjusted to its maximum redemption value at each reporting date when the maximum redemption value is greater than the initial carrying amount of the RNCI. For the period of time that the DPLTA is in effect, the RNCI will continue to be presented as RNCI outside of stockholders’ equity in the Condensed Consolidated Balance Sheets. See Note 14 for additional information on RNCI .
Recent Accounting Pronouncements Not Yet Adopted	Recent Accounting Pronouncements Not Yet Adopted In November 2024, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") 2024-03, "Disaggregation of Income Statement Expenses (DISE) (Topic 220): Improvements to Income Statement Disclosures", which applies to all public business entities (PBEs) and is intended to enhance disclosures about specific types of expenses included in the expense captions presented on the face of the income statement as well as disclosures about selling expenses. The amendments are effective prospectively for annual periods beginning after December 15, 2026, and early adoption and retrospective application are permitted. The Company is currently evaluating the effect that adoption of ASU 2024-03 will have on our disclosures. In December 2023, the Financial Accounting Standards Board (“FASB”) issued Accounting Standards Update ("ASU") 2023-09, "Income Taxes (Topic 740): Improvements to Income Tax Disclosures", which is intended to enhance the transparency, decision usefulness and effectiveness of income tax disclosures. The amendments in this ASU require a public entity to disclose a tabular tax rate reconciliation, using both percentages and currency, with specific categories. A public entity is also required to provide a qualitative description of the states and local jurisdictions that make up the majority of the effect of the state and local income tax category and the net amount of income taxes paid, disaggregated by federal, state and foreign taxes and also disaggregated by individual jurisdictions. The amendments also remove certain disclosures that are no longer considered cost beneficial. The amendments are effective prospectively for annual periods beginning after December 15, 2024, and early adoption and retrospective application are permitted. The Company is currently evaluating the effect that adoption of ASU 2023-09 will have on our disclosures. In November 2023, the FASB issued ASU 2023-7, "Segment Reporting (Topic 280): Improvements to Reportable Segment Disclosures", which is intended to improve reportable segment disclosure requirements, primarily through enhanced disclosures about significant segment expenses, allowing financial statement users to better understand the components of a segment's profit or loss to assess potential future cash flows for each reportable segment and the entity as a whole. The amendments expand a public entity's segment disclosures by requiring disclosure of significant segment expenses that are regularly provided to the chief operating decision maker ("CODM"), clarifying when an entity may report one or more additional measures to assess segment performance, requiring enhanced interim disclosures, providing new disclosure requirements for entities with a single reportable segment, and requiring other new disclosures. The amendments are effective for fiscal years beginning after December 15, 2023, and interim periods within fiscal years beginning after December 15, 2024, and early adoption is permitted. The Company expects to adopt the new disclosures as required for the year ended December 31, 2024. The Company is currently evaluating the impact on the related disclosures.
Recently Adopted Accounting Pronouncements	Recently Adopted Accounting Pronouncements There are currently no recently adopted accounting pronouncements that are expected to have a material effect on the Condensed Consolidated Financial Statements.

Summary of Significant Accoun_3

Summary of Significant Accounting Policies (Tables)	9 Months Ended
	Sep. 30, 2024
Accounting Policies [Abstract]
Summary of Impact of Revision to Specific Line Items in Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Loss, Condensed Consolidated Statements of Comprehensive Loss, and Condensed Consolidated Statements of Changes in Stockholders	The following tables reflect the impact of the revision to the specific line items presented in the Company's previously reported Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Loss, and Condensed Consolidated Statements of Comprehensive Loss for the for fiscal periods beginning with the quarter ended March 31, 2023 through the quarter ended June 30, 2024. March 31, 2023 (In thousands) As Previously Reported Revision As Revised Other non-current liabilities $ 15,986 $ ( 346 ) (a) $ 15,640 Total Liabilities $ 675,765 $ (346 ) $ 675,419 Redeemable Non-Controlling Interest $ 442,668 $ ( 430 ) (b) $ 442,238 Accumulated Other Comprehensive Income $ 34,526 $ 1 (a) $ 34,527 Retained Earnings $ 8,006 $ 775 (a)(b) $ 8,781 Total Equity $ 820,162 $ 776 $ 820,938 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,938,595 $ — $ 1,938,595 For the Three Months Ended March 31, 2023 (In thousands) As Previously Reported Revision As Revised Less: Net Loss attributable to non-controlling interest $ ( 370 ) $ ( 345 ) (a) $ ( 715 ) Net Loss attributable to ADTRAN Holdings, Inc. $ ( 40,083 ) $ 345 (a) $ ( 39,738 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.51 ) $ — $ ( 0.51 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.51 ) $ — $ ( 0.51 ) Foreign currency translation gain $ 8,678 $ 1 (a) $ 8,679 Other Comprehensive Income, net of tax $ 8,782 $ 1 $ 8,783 Comprehensive Loss, net of tax $ ( 31,671 ) $ 1 $ ( 31,670 ) Less: Comprehensive Income (Loss) attributable to non-controlling interest, net of tax $ 12 $ ( 345 ) (a) $ ( 333 ) Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 31,683 ) $ 346 (a) $ ( 31,337 ) June 30, 2023 (In thousands) As Previously Reported Revision As Revised Other non-current liabilities $ 16,401 $ ( 695 ) (a) $ 15,706 Total Liabilities $ 665,006 $ (695 ) $ 664,311 Redeemable Non-Controlling Interest $ 445,462 $ ( 3,244 ) (b) $ 442,218 Accumulated Other Comprehensive Income $ 41,483 $ 2 (a) $ 41,485 Retained Deficit $ ( 41,010 ) $ 3,937 (a)(b) $ ( 37,073 ) Total Equity $ 782,470 $ 3,939 $ 786,409 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,882,938 $ — $ 1,882,938 For the Three Months Ended June 30, 2023 For the Six Months Ended June 30, 2023 (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,882 $ ( 348 ) (a) $ 2,534 $ 2,512 $ ( 693 ) (a) $ 1,819 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 39,097 ) $ 348 (a) $ ( 38,749 ) $ ( 79,180 ) $ 693 (a) $ ( 78,487 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.50 ) $ — $ ( 0.50 ) $ ( 1.01 ) $ 0.01 (a) $ ( 1.00 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.50 ) $ — $ ( 0.50 ) $ ( 1.01 ) $ 0.01 (a) $ ( 1.00 ) Foreign currency translation gain $ 6,940 $ 1 (a) $ 6,941 $ 15,618 $ 2 (a) $ 15,620 Other Comprehensive Income, net of tax $ 6,957 $ 1 $ 6,958 $ 15,739 $ 2 $ 15,741 Comprehensive Loss, net of tax $ ( 29,258 ) $ 1 $ ( 29,257 ) $ ( 60,929 ) $ 2 $ ( 60,927 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,882 $ ( 348 ) (a) $ 2,534 $ 2,894 $ ( 693 ) (a) $ 2,201 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 32,140 ) $ 349 (a) $ ( 31,791 ) $ ( 63,823 ) $ 695 (a) $ ( 63,128 ) September 30, 2023 (In thousands) As Previously Reported Revision As Revised Other non-current liabilities $ 17,408 $ ( 1,049 ) (a) $ 16,359 Total Liabilities $ 625,355 $ (1,049 ) $ 624,306 Redeemable Non-Controlling Interest $ 431,921 $ 10,291 (b) $ 442,212 Accumulated Other Comprehensive Income $ 12,075 $ 3 (a) $ 12,078 Retained Deficit $ ( 113,289 ) $ ( 9,245 ) (a)(b) $ ( 122,534 ) Total Equity $ 684,893 $ ( 9,242 ) $ 675,651 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,742,169 $ — $ 1,742,169 For the Three Months Ended September 30, 2023 For the Nine Months Ended September 30, 2023 (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,914 $ ( 353 ) (a) $ 2,561 $ 5,426 $ ( 1,046 ) (a) $ 4,380 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 78,563 ) $ 353 (a) $ ( 78,210 ) $ ( 157,743 ) $ 1,046 (a) $ ( 156,697 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 1.00 ) $ — $ ( 1.00 ) $ ( 2.01 ) $ 0.01 (a) $ ( 2.00 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 1.00 ) $ — $ ( 1.00 ) $ ( 2.01 ) $ 0.01 (a) $ ( 2.00 ) Foreign currency translation loss $ ( 29,716 ) $ 1 (a) $ ( 29,715 ) $ ( 14,098 ) $ 3 (a) $ ( 14,095 ) Other Comprehensive Loss, net of tax $ ( 29,408 ) $ 1 $ ( 29,407 ) $ ( 13,669 ) $ 3 $ ( 13,666 ) Comprehensive Loss, net of tax $ ( 105,057 ) $ 1 $ ( 105,056 ) $ ( 165,986 ) $ 3 $ ( 165,983 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,914 $ ( 353 ) (a) $ 2,561 $ 5,808 $ ( 1,046 ) (a) $ 4,762 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 107,971 ) $ 354 (a) $ ( 107,617 ) $ ( 171,794 ) $ 1,049 (a) $ ( 170,745 ) March 31, 2024 (In thousands) As Previously Reported Revision As Revised Accrued Expenses and Other Liabilities $ 36,404 $ ( 1,403 ) (a) $ 35,001 Total Current Liabilities $ 282,746 $ (1,403 ) $ 281,343 Other non-current liabilities $ 35,375 $ (350 ) (a) $ 35,025 Total Liabilities $ 620,488 $ (1,753 ) $ 618,735 Redeemable Non-Controlling Interest $ 441,635 $ 511 (b) $ 442,146 Accumulated Other Comprehensive Income $ 29,656 $ 5 (a) $ 29,661 Retained Deficit $ ( 558,363 ) $ 1,237 (a)(b) $ ( 557,126 ) Total Equity $ 265,783 $ 1,242 $ 267,025 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,327,906 $ — $ 1,327,906 For the Three Months Ended March 31, 2024 (In thousands) As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,880 $ ( 349 ) (a) $ 2,531 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 324,550 ) $ 349 (a) $ ( 324,201 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 4.12 ) $ — $ ( 4.12 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 4.12 ) $ — $ ( 4.12 ) Foreign currency translation loss $ ( 17,745 ) $ 1 (a) $ ( 17,744 ) Other Comprehensive Loss, net of tax $ ( 17,805 ) $ 1 $ ( 17,804 ) Comprehensive Loss, net of tax $ ( 339,475 ) $ 1 $ ( 339,474 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,880 $ ( 349 ) (a) $ 2,531 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 342,355 ) $ 350 (a) $ ( 342,005 ) June 30, 2024 (In thousands) As Previously Reported Revision As Revised Accrued Expenses and Other Liabilities $ 36,307 $ ( 1,403 ) (a) $ 34,904 Total Current Liabilities $ 289,712 $ (1,403 ) $ 288,309 Other non-current liabilities $ 34,445 $ (701 ) (a) $ 33,744 Total Liabilities $ 630,810 $ (2,104 ) $ 628,706 Redeemable Non-Controlling Interest $ 439,743 $ 2,379 (b) $ 442,122 Accumulated Other Comprehensive Income $ 28,274 $ 6 (a) $ 28,280 Retained Deficit $ ( 606,375 ) $ ( 281 ) (a)(b) $ ( 606,656 ) Total Equity $ 220,229 $ ( 275 ) $ 219,954 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,290,782 $ — $ 1,290,782 For the Three Months Ended June 30, 2024 For the Six Months Ended June 30, 2024 (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 2,854 $ ( 350 ) (a) $ 2,504 $ 5,734 $ ( 699 ) (a) $ 5,035 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 49,865 ) $ 350 (a) $ ( 49,515 ) $ ( 374,415 ) $ 699 (a) $ ( 373,716 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.63 ) $ — $ ( 0.63 ) $ ( 4.75 ) $ 0.01 (a) $ ( 4.74 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.63 ) $ — $ ( 0.63 ) $ ( 4.75 ) $ 0.01 (a) $ ( 4.74 ) Foreign currency translation loss $ ( 1,375 ) $ 1 (a) $ ( 1,374 ) $ ( 19,120 ) $ 2 (a) $ ( 19,118 ) Other Comprehensive Loss, net of tax $ ( 1,382 ) $ 1 $ ( 1,381 ) $ ( 19,187 ) $ 2 $ ( 19,185 ) Comprehensive Loss, net of tax $ ( 48,393 ) $ 1 $ ( 48,392 ) $ ( 387,868 ) $ 2 $ ( 387,866 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 2,854 $ ( 350 ) (a) $ 2,504 $ 5,734 $ ( 699 ) (a) $ 5,035 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 51,247 ) $ 351 (a) $ ( 50,896 ) $ ( 393,602 ) $ 701 (a) $ ( 392,901 ) The following tables reflect the impact of the revisions to the specific line items presented in the Company’s previously reported Consolidated Balance Sheet as of December 31, 2023, the Consolidated Statement of Loss and the Consolidated Statement of Comprehensive Loss for the year ended December 31, 2023. December 31, 2023 (In thousands) As Previously Reported Revision As Revised Accrued Expenses and Other Liabilities $ 37,607 $ ( 1,403 ) (a) $ 36,204 Total Current Liabilities $ 279,511 $ (1,403 ) $ 278,108 Total Liabilities $ 636,934 $ (1,403 ) $ 635,531 Redeemable Non-Controlling Interest $ 451,756 $ ( 9,604 ) (b) $ 442,152 Accumulated Other Comprehensive Income $ 47,461 $ 4 (a) $ 47,465 Retained Deficit $ ( 243,908 ) $ 11,003 (a)(b) $ ( 232,905 ) Total Equity $ 593,822 $ 11,007 $ 604,829 Total Liabilities, Redeemable Non-Controlling Interest and Equity $ 1,682,512 $ — $ 1,682,512 For the Year Ended December 31, 2023 (In thousands) As Previously Reported Revision As Revised Less: Net Income attributable to non-controlling interest $ 8,345 $ ( 1,399 ) (a) $ 6,946 Net Loss attributable to ADTRAN Holdings, Inc. $ ( 267,688 ) $ 1,399 (a) $ ( 266,289 ) Loss per common share attributable to ADTRAN Holdings, Inc. – basic $ ( 3.41 ) $ 0.02 (a) $ ( 3.39 ) Loss per common share attributable to ADTRAN Holdings, Inc. – diluted $ ( 3.41 ) $ 0.02 (a) $ ( 3.39 ) Foreign currency translation gain $ 22,753 $ 4 (a) $ 22,757 Other Comprehensive Income, net of tax $ 21,717 $ 4 $ 21,721 Comprehensive Loss, net of tax $ ( 237,626 ) $ 4 $ ( 237,622 ) Less: Comprehensive Income attributable to non-controlling interest, net of tax $ 8,727 $ ( 1,399 ) (a) $ 7,328 Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax $ ( 246,353 ) $ 1,403 (a) $ ( 244,950 ) The following tables reflect the impact of the revision to the specific line items presented in the Company's previously reported Condensed Consolidated Statements of Changes in Stockholders Equity as of September 30, 2023 and 2024: Retained Earnings (Deficit) Accumulated Other Comprehensive Income (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Annual recurring compensation earned $ ( 2,809 ) $ 345 (a) $ ( 2,464 ) $ - $ - $ - Other comprehensive income, net of tax $ - $ - $ - $ 8,400 $ 1 (a) $ 8,401 Foreign currency remeasurement of redeemable non-controlling interest $ ( 430 ) $ 430 (b) $ - $ - $ - $ - Balance as of March 31, 2023 $ 8,006 $ 775 $ 8,781 $ 34,526 $ 1 $ 34,527 Annual recurring compensation earned $ ( 2,882 ) $ 348 (a) $ ( 2,534 ) $ - $ - $ - Other comprehensive income, net of tax $ - $ - $ - $ 6,957 $ 1 (a) $ 6,958 Foreign currency remeasurement of redeemable non-controlling interest $ ( 2,814 ) $ 2,814 (b) $ - $ - $ - $ - Balance as of June 30, 2023 $ ( 41,010 ) $ 3,937 $ ( 37,073 ) $ 41,483 $ 2 $ 41,485 Annual recurring compensation earned $ ( 2,914 ) $ 353 (a) $ ( 2,561 ) $ - $ - $ - Other comprehensive loss, net of tax $ - $ - $ - $ ( 29,408 ) $ 1 (a) $ ( 29,407 ) Foreign currency remeasurement of redeemable non-controlling interest $ 13,535 $ ( 13,535 ) (b) $ - $ - $ - $ - Balance as of September 30, 2023 $ ( 113,289 ) $ ( 9,245 ) $ ( 122,534 ) $ 12,075 $ 3 $ 12,078 Retained Deficit Accumulated Other Comprehensive Income (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Balance as of December 31, 2023 $ ( 243,908 ) $ 11,003 (a) $ ( 232,905 ) $ 47,461 $ 4 (a) $ 47,465 Annual recurring compensation earned $ ( 2,880 ) $ 349 (a) $ ( 2,531 ) $ - $ - $ - Other comprehensive loss, net of tax $ - $ - $ - $ ( 17,805 ) $ 1 (a) $ ( 17,804 ) Foreign currency remeasurement of redeemable non-controlling interest $ 10,115 $ ( 10,115 ) (b) $ - $ - $ - $ - Balance as of March 31, 2024 $ ( 558,363 ) $ 1,237 $ ( 557,126 ) $ 29,656 $ 5 $ 29,661 Annual recurring compensation earned $ ( 2,854 ) $ 350 (a) $ ( 2,504 ) $ - $ - Other comprehensive loss, net of tax $ - $ - $ - $ ( 1,382 ) $ 1 (a) $ ( 1,381 ) Foreign currency remeasurement of redeemable non-controlling interest $ 1,868 $ ( 1,868 ) (b) $ - $ - $ - $ - Balance as of June 30, 2024 $ ( 606,375 ) $ ( 281 ) $ ( 606,656 ) $ 28,274 $ 6 $ 28,280 The following tables reflect the impact of the revision to the specific line items presented in the Company's previously reported Consolidated Statement of Changes in Stockholders as of December 31, 2023: Retained Earnings (Deficit) Accumulated Other Comprehensive Income (In thousands) As Previously Reported Revision As Revised As Previously Reported Revision As Revised Annual recurring compensation earned $ ( 11,524 ) $ 1,399 (a) $ ( 10,125 ) $ - $ - $ - Other comprehensive income, net of tax $ - $ - $ - $ 21,335 $ 4 (a) $ 21,339 Foreign currency remeasurement of redeemable non-controlling interest $ ( 9,604 ) $ 9,604 (b) $ - $ - $ - $ - Balance as of December 31, 2023 $ ( 243,908 ) $ 11,003 $ ( 232,905 ) $ 47,461 $ 4 $ 47,465

Revenue (Tables)

Revenue (Tables)	9 Months Ended
	Sep. 30, 2024
Revenue from Contract with Customer [Abstract]
Disaggregate of Revenue by Reportable Segment and Revenue Category	The following tables disaggregate revenue by reportable segment and revenue category: Three Months Ended September 30, 2024 September 30, 2023 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Subscriber Solutions $ 81,060 $ 9,036 $ 90,096 $ 52,921 $ 8,564 $ 61,485 Optical Networking Solutions 47,474 23,061 70,535 94,592 21,608 116,200 Access & Aggregation Solutions 52,954 14,119 67,073 81,051 13,595 94,646 Total $ 181,488 $ 46,216 $ 227,704 $ 228,564 $ 43,767 $ 272,331 Nine Months Ended September 30, 2024 September 30, 2023 (In thousands) Network Solutions Services & Support Total Network Solutions Services & Support Total Subscriber Solutions $ 215,044 $ 27,218 $ 242,262 $ 196,726 $ 25,760 $ 222,486 Optical Networking Solutions 152,068 67,246 219,314 342,390 64,562 406,952 Access & Aggregation Solutions 174,843 43,449 218,292 254,868 39,315 294,183 Total $ 541,955 $ 137,913 $ 679,868 $ 793,984 $ 129,637 $ 923,621
Information about Receivable, Contract Assets, and Unearned Revenue from Contracts with Customers	The following table provides information about accounts receivable, contract assets and unearned revenue from contracts with customers: As of As of (In thousands) September 30, 2024 December 31, 2023 Accounts receivable, net $ 172,025 $ 216,445 Contract assets (1) $ 668 $ 691 Unearned revenue $ 54,615 $ 46,731 Non-current unearned revenue $ 24,901 $ 25,109 (1) Included in other receivables on the Condensed Consolidated Balance Sheets.

Stock-Based Compensation (Table

Stock-Based Compensation (Tables)	9 Months Ended
	Sep. 30, 2024
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Stock-Based Compensation Expense Related to Stock Options, PSUs, RSUs and Restricted Stock	The following table summarizes the PSUs, RSUs and restricted stock outstanding as of December 31, 2023, and September 30, 2024 and the changes that occurred during the nine months ended September 30, 2024: Number of Weighted Avg. Grant Date Fair Value Unvested PSUs, RSUs and restricted stock outstanding, December 31, 2023 1,942 $ 17.46 PSUs, RSUs and restricted stock granted 1,097 $ 7.85 PSUs, RSUs and restricted stock vested ( 263 ) $ 18.86 PSUs, RSUs and restricted stock forfeited ( 111 ) $ 14.25 Unvested PSUs, RSUs and restricted stock outstanding, September 30, 2024 2,665 $ 13.50
Summary of Stock Options Outstanding	The following table summarizes the ADTRAN Holdings, Inc. stock options outstanding as of December 31, 2023, and September 30, 2024, and the changes that occurred during the nine months ended September 30, 2024: Number of Weighted Avg. Weighted Avg. Aggregate Stock options outstanding, December 31, 2023 3,894 $ 10.32 5.25 $ 3,087 Stock options exercised ( 36 ) $ 6.06 Stock options forfeited ( 171 ) $ 6.68 Stock options expired ( 243 ) $ 9.31 Stock options outstanding, September 30, 2024 3,444 $ 10.61 4.64 $ 829 Stock options exercisable, September 30, 2024 1,342 $ 12.63 1.11 $ —

Investments (Tables)

Investments (Tables)	9 Months Ended
	Sep. 30, 2024
Investments, Debt and Equity Securities [Abstract]
Gross Realized Gains and Losses on Sale of Debt Securities	The following tab le presents the gross realized gains and losses related to its debt securities: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Gross realized gain on debt securities $ — $ 5 $ — $ 9 Gross realized loss on debt securities — ( 317 ) — ( 355 ) Total loss recognized, net $ — $ ( 312 ) $ — $ ( 346 )
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 Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Unrealized gain (loss) on equity securities held $ 1,372 $ ( 1,130 ) $ 4,371 $ 1,404 Realized (loss) gain on equity securities sold 10 ( 1 ) 136 13 Total gain (loss) recognized, net $ 1,382 $ ( 1,131 ) $ 4,507 $ 1,417
Cash Equivalents and Investments held at Fair Value	The Company’s cash equivalents and investments held at fair value are categorized into this hierarchy as follows: Fair Value Measurements as of September 30, 2024 Using (In thousands) Fair Value Quoted Prices Significant Significant Unobservable Inputs Cash equivalents Money market funds $ 5,500 $ 5,500 $ — $ — Marketable equity securities Marketable equity securities – various industries 1,035 1,035 — — Deferred compensation plan assets 30,471 30,471 — — Total $ 37,006 $ 37,006 $ — $ — Fair Value Measurements as of December 31, 2023 Using (In thousands) Fair Value Quoted Prices Significant Significant Unobservable Inputs Cash equivalents Money market funds $ 5,302 $ 5,302 $ — $ — Marketable equity securities Marketable equity securities – various industries 905 905 — — Deferred compensation plan assets 26,838 26,838 — — Total $ 33,045 $ 33,045 $ — $ —

Inventory (Tables)

Inventory (Tables)	9 Months Ended
	Sep. 30, 2024
Inventory Disclosure [Abstract]
Components of Inventory	Inventory consisted of the following: As of As of (In thousands) September 30, 2024 December 31, 2023 Raw materials $ 114,873 $ 152,140 Work in process 10,942 17,239 Finished goods 157,111 192,916 Total inventory, net $ 282,926 $ 362,295

Property, Plant and Equipment (

Property, Plant and Equipment (Tables)	9 Months Ended
	Sep. 30, 2024
Property, Plant and Equipment [Abstract]
Property, Plant and Equipment	Property, plant and equipment consisted of the following: As of As of (In thousands) September 30, 2024 December 31, 2023 Engineering and other equipment $ 187,753 $ 183,336 Building 79,857 79,215 Computer hardware and software 139,006 101,572 Building and land improvements 59,487 58,238 Furniture and fixtures 21,542 21,368 Land 5,248 5,242 Total property, plant and equipment 492,893 448,971 Less: accumulated depreciation ( 345,465 ) ( 325,951 ) Total property, plant and equipment, net $ 147,428 $ 123,020

Goodwill (Tables)

Goodwill (Tables)	9 Months Ended
	Sep. 30, 2024
Goodwill Disclosure [Abstract]
Summary of Changes in Carrying Amount of Goodwill	The changes in the carrying amount of goodwill for the nine months ended September 30, 2024, are as follows: (In thousands) Network Solutions Services & Support Total As of December 31, 2023 $ 297,031 $ 56,384 $ 353,415 Goodwill impairment ( 290,528 ) — ( 290,528 ) Foreign currency translation adjustments ( 6,503 ) 500 ( 6,003 ) As of September 30, 2024 $ — $ 56,884 $ 56,884

Intangible Assets (Tables)

Intangible Assets (Tables)	9 Months Ended
	Sep. 30, 2024
Intangible Assets, Net (Excluding Goodwill) [Abstract]
Summary of Intangible Assets	Intangible assets consisted of the following: As of September 30, 2024 As of December 31, 2023 (In thousands) Weighted Average Useful Life Gross Carrying Amount Accumulated Amortization Net Book Value Gross Carrying Amount Accumulated Amortization Net Book Value Developed technology 8.5 $ 332,245 $ ( 91,210 ) $ 241,035 $ 329,369 $ ( 61,271 ) $ 268,098 Customer relationships 10.9 $ 54,016 $ ( 18,461 ) $ 35,555 $ 54,856 $ ( 15,943 ) $ 38,913 Trade names 3.0 29,955 ( 24,993 ) 4,962 29,689 ( 16,379 ) 13,310 Backlog 1.6 57,905 ( 55,133 ) 2,772 57,391 ( 52,022 ) 5,369 Licensed technology 9.0 5,900 ( 4,288 ) 1,612 5,900 ( 3,797 ) 2,103 Licensing agreements 8.5 560 ( 398 ) 162 560 ( 368 ) 192 Patents 7.3 — — — 500 ( 500 ) — Total $ 480,581 $ ( 194,483 ) $ 286,098 $ 478,265 $ ( 150,280 ) $ 327,985
Estimated Future Amortization Expense Related to Intangible Assets	Estimated future amortization expense of intangible assets is as follows: As of (In thousands) September 30, 2024 2024 $ 14,905 2025 47,737 2026 44,408 2027 43,018 2028 42,870 Thereafter 93,160 Total $ 286,098

Hedging (Tables)

Hedging (Tables)	9 Months Ended
	Sep. 30, 2024
Derivative Instruments and Hedging Activities Disclosure [Abstract]
Schedule of Fair Values of Derivative Instruments	The fair values of the Company's derivative instruments recorded in the Condensed Consolidated Balance Sheet as of September 30, 2024 and December 31, 2023 were as follows: (In thousands) Balance Sheet Location September 30, 2024 December 31, 2023 Derivatives Not Designated as Hedging Instruments (Level 2): Foreign exchange contracts – derivative assets Other receivables $ 1,712 $ 7,125 Foreign exchange contracts – derivative liabilities Accounts payable $ ( 1,030 ) $ ( 2,277 ) Total derivatives $ 682 $ 4,848 The change in the fair values of the Company's derivative instruments recorded in the Condensed Consolidated Statements of Loss during the three and nine months ended September 30, 2024 and 2023 were as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) Income Statement 2024 2023 2024 2023 Derivatives Not Designated as Hedging Instruments: Foreign exchange contracts Other (expense) income, net $ ( 411 ) $ 1,012 $ ( 380 ) $ 1,076

Credit Agreements (Tables)

Credit Agreements (Tables)	9 Months Ended
	Sep. 30, 2024
Debt Disclosure [Abstract]
Carrying Amount of Non-Current Revolving Facility	The carrying amounts of the Company's non-current revolving credit facility in its Condensed Consolidated Balance Sheets were as follows: As of As of (In thousands) September 30, 2024 December 31, 2023 Wells Fargo credit agreement $ 189,849 $ 195,000 Total non-current revolving credit facility $ 189,849 $ 195,000

Employee Benefit Plans (Tables)

Employee Benefit Plans (Tables)	9 Months Ended
	Sep. 30, 2024
Retirement Benefits [Abstract]
Schedule of the Components of Net Periodic Pension Cost	The following table summarizes the components of net periodic pension cost related to the Company's defined benefit pension plans: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Service cost $ 340 $ 401 $ 1,013 $ 1,203 Interest cost 286 ( 33 ) 852 ( 99 ) Expected return on plan assets ( 360 ) 59 ( 1,074 ) 177 Amortization of actuarial losses 2 7 7 20 Net periodic pension cost $ 268 $ 434 $ 798 $ 1,301

Equity (Tables)

Equity (Tables)	9 Months Ended
	Sep. 30, 2024
Equity [Abstract]
Changes in Accumulated Other Comprehensive Income, Net of Tax, by Component	The following tables present the changes in accumulated other comprehensive income, net of tax, by component: Three Months Ended September 30, 2024 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of June 30, 2024 $ ( 382 ) $ ( 2,573 ) $ 30,850 $ 385 $ 28,280 Other comprehensive (loss) income before ( 10 ) — 18,988 — 18,978 Amounts reclassified from accumulated other 10 109 — — 119 Net current period other comprehensive gain — 109 18,988 — 19,097 Balance as of September 30, 2024 $ ( 382 ) $ ( 2,464 ) $ 49,838 $ 385 $ 47,377 Three Months Ended September 30, 2023 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of June 30, 2023 $ ( 773 ) $ ( 958 ) $ 42,831 $ 385 $ 41,485 Other comprehensive income (loss) before 635 — ( 29,715 ) — ( 29,080 ) Amounts reclassified from accumulated other ( 244 ) ( 83 ) — — ( 327 ) Net current period other comprehensive income (loss) 391 ( 83 ) ( 29,715 ) — ( 29,407 ) Less: Comprehensive income attributable to non-controlling interest, net of tax — — — — — Balance as of September 30, 2023 $ ( 382 ) $ ( 1,041 ) $ 13,116 $ 385 $ 12,078 Nine Months Ended September 30, 2024 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of December 31, 2023 $ ( 382 ) $ ( 2,506 ) $ 49,968 $ 385 $ 47,465 Other comprehensive loss before ( 134 ) — ( 130 ) — ( 264 ) Amounts reclassified from accumulated other 134 42 — — 176 Net current period other comprehensive income (loss) — 42 ( 130 ) — ( 88 ) Balance as of September 30, 2024 $ ( 382 ) $ ( 2,464 ) $ 49,838 $ 385 $ 47,377 Nine Months Ended September 30, 2023 (In thousands) Unrealized Defined Foreign ASU 2018-02 Adoption Total Balance as of December 31, 2022 $ ( 836 ) $ ( 1,016 ) $ 27,593 $ 385 $ 26,126 Other comprehensive income (loss) before 733 — ( 14,095 ) — ( 13,362 ) Amounts reclassified from accumulated other ( 279 ) ( 25 ) — — ( 304 ) Net current period other comprehensive income (loss) 454 ( 25 ) ( 14,095 ) — ( 13,666 ) Less: Comprehensive income attributable to non-controlling — — 382 — 382 Balance as of September 30, 2023 $ ( 382 ) $ ( 1,041 ) $ 13,116 $ 385 $ 12,078
Reclassifications Out of Accumulated Other Comprehensive Income	The following tables present the details of reclassifications out of accumulated other comprehensive income: Three Months Ended September 30, 2024 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized loss on sales of securities $ ( 13 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial loss ( 158 ) (1) Total reclassifications for the period, before tax ( 171 ) Tax expense 52 Total reclassifications for the period, net of tax $ ( 119 ) (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. Three Months Ended September 30, 2023 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized gain on sales of securities $ 321 Net investment gain (loss) Defined benefit plan adjustments – actuarial gain 120 (1) Total reclassifications for the period, before tax 441 Tax benefit ( 114 ) Total reclassifications for the period, net of tax $ 327 (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. Nine Months Ended September 30, 2024 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized loss on sales of securities $ ( 181 ) Net investment gain (loss) Defined benefit plan adjustments – actuarial loss ( 61 ) (1) Total reclassifications for the period, before tax ( 242 ) Tax expense 66 Total reclassifications for the period, net of tax $ ( 176 ) (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. Nine Months Ended September 30, 2023 (In thousands) Amount Affected Line Item in the Unrealized gain (loss) on available-for-sale securities: Net realized gain on sales of securities $ 367 Net investment gain (loss) Defined benefit plan adjustments – actuarial gain 36 (1) Total reclassifications for the period, before tax 403 Tax benefit ( 99 ) Total reclassifications for the period, net of tax $ 304 (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.
Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Loss)	The following table presents the tax effects related to the change in each component of other comprehensive (loss) income: Three Months Ended Three Months Ended September 30, 2024 September 30, 2023 (In thousands) Before-Tax Tax Net-of-Tax Before-Tax Tax Net-of-Tax Unrealized (loss) gain on available-for-sale $ ( 13 ) $ 3 $ ( 10 ) $ 836 $ ( 201 ) $ 635 Reclassification adjustment for amounts related to available-for-sale investments included in net gain (loss) 13 ( 3 ) 10 ( 321 ) 77 ( 244 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net gain (loss) 158 ( 49 ) 109 ( 120 ) 37 ( 83 ) Foreign currency translation adjustments 18,988 — 18,988 ( 29,715 ) — ( 29,715 ) Total Other Comprehensive Income (Loss) $ 19,146 $ ( 49 ) $ 19,097 $ ( 29,320 ) $ ( 87 ) $ ( 29,407 ) Nine Months Ended Nine Months Ended September 30, 2024 September 30, 2023 (In thousands) Before-Tax Tax Net-of-Tax Before-Tax Tax Net-of-Tax Unrealized (loss) gain on available-for-sale $ ( 181 ) $ 47 $ ( 134 ) $ 964 $ ( 231 ) $ 733 Reclassification adjustment for amounts related to available-for-sale investments included in net gain (loss) 181 ( 47 ) 134 ( 367 ) 88 ( 279 ) Reclassification adjustment for amounts related to defined benefit plan adjustments included in net gain (loss) 61 ( 19 ) 42 ( 36 ) 11 ( 25 ) Foreign currency translation adjustments ( 130 ) — ( 130 ) ( 14,095 ) — ( 14,095 ) Total Other Comprehensive Loss $ ( 69 ) $ ( 19 ) $ ( 88 ) $ ( 13,534 ) $ ( 132 ) $ ( 13,666 )

Redeemable Non-controlling In_2

Redeemable Non-controlling Interest (Tables)	9 Months Ended
	Sep. 30, 2024
Redeemable Noncontrolling Interest, Equity, Carrying Amount [Abstract]
Summary of Redeemable Non-controlling Interest Activity	The following table summarizes the redeemable non-controlling interest activity for the nine months ended September 30, 2024 and for the year ended December 31, 2023: Nine Months Ended For the Year Ended (In thousands) September 30, 2024 December 31, 2023 Balance at beginning of period $ 442,152 $ — Reclassification of non-controlling interests — 443,757 Redemption of redeemable non-controlling interest ( 20,376 ) ( 1,657 ) Net income attributable to redeemable non-controlling interests 7,417 10,092 (1) Annual recurring compensation earned ( 7,417 ) ( 10,092 ) (1) Adtran Networks stock option exercises — 52 Balance at end of period $ 421,776 $ 442,152 (1) (1) Following the third quarter of 2024, the Company identified errors primarily impacting the carrying values of the redeemable non-controlling interest, retained deficit, the net income attributable to the non-controlling interest and the net loss attributable to the Company and, as a consequence, of the loss per common share attributable to the Company. We have revised our previously issued Condensed Consolidated Financial Statements for the periods ended March 31, 2023, June 30, 2023, September 30, 2023, December 31, 2023, March 31, 2024 and June 30, 2024. See Note 1 for additional information.

Loss Per Share (Tables)

Loss Per Share (Tables)	9 Months Ended
	Sep. 30, 2024
Earnings Per Share [Abstract]
Summary of Calculation of Basic and Diluted Loss Per Share	The calculation of basic and diluted loss per share is as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands, except per share amounts) 2024 2023 2024 2023 Numerator Net loss attributable to ADTRAN Holdings, Inc. $ ( 31,239 ) $ ( 78,210 ) $ ( 404,955 ) $ ( 156,697 ) Effect of redemption of RNCI 2,976 — 2,976 — Net loss attributable to ADTRAN Holdings, Inc. common shareholders $ ( 28,263 ) $ ( 78,210 ) $ ( 401,979 ) $ ( 156,697 ) Denominator Weighted average number of shares – basic 78,952 78,389 78,873 78,378 Effect of dilutive securities Stock options — — — — PSUs, RSUs and restricted stock — — — — Weighted average number of shares – diluted 78,952 78,389 78,873 78,378 Loss per share attributable to ADTRAN Holdings, Inc. – basic $ ( 0.36 ) $ ( 1.00 ) $ ( 5.10 ) $ ( 2.00 ) Loss per share attributable to ADTRAN Holdings, Inc. – diluted $ ( 0.36 ) $ ( 1.00 ) $ ( 5.10 ) $ ( 2.00 )

Segment Information (Tables)

Segment Information (Tables)	9 Months Ended
	Sep. 30, 2024
Segment Reporting [Abstract]
Revenue and Gross Profit of Reportable Segments	The following tables present information about the revenue and gross profit of the Company's reportable segments: Three Months Ended September 30, 2024 September 30, 2023 (In thousands) Revenue Gross Profit Revenue Gross Profit Network Solutions $ 181,488 $ 55,713 $ 228,564 $ 47,277 Services & Support 46,216 29,538 43,767 26,960 Total $ 227,704 $ 85,251 $ 272,331 $ 74,237 Nine Months Ended September 30, 2024 September 30, 2023 (In thousands) Revenue Gross Profit Revenue Gross Profit Network Solutions $ 541,955 $ 156,472 $ 793,984 $ 176,607 Services & Support 137,913 82,609 129,637 77,991 Total $ 679,868 $ 239,081 $ 923,621 $ 254,598
Revenue Information by Geographic Area	The following table presents revenue information by geographic area: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 United States $ 102,527 $ 111,494 $ 293,420 $ 375,254 United Kingdom 49,366 60,347 145,666 212,171 Germany 27,270 41,242 91,553 150,710 Other international 48,541 59,248 149,229 185,486 Total $ 227,704 $ 272,331 $ 679,868 $ 923,621

Liability for Warranty Returns

Liability for Warranty Returns (Tables)	9 Months Ended
	Sep. 30, 2024
Product Warranties Disclosures [Abstract]
Summary of Warranty Expense and Write-off Activity	The warranty expense and write-off activity for the three and nine months ended September 30, 2024 and 2023 are summarized as follows: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Balance at beginning of period $ 6,024 $ 6,831 $ 6,445 $ 7,196 Plus: Amounts charged to cost and expenses 395 752 1,779 2,289 Plus: Foreign currency translation adjustments 84 ( 73 ) 21 ( 33 ) Less: Deductions ( 854 ) ( 943 ) ( 2,596 ) ( 2,885 ) Balance at end of period $ 5,649 $ 6,567 $ 5,649 $ 6,567

Restructuring (Tables)

Restructuring (Tables)	9 Months Ended
	Sep. 30, 2024
Restructuring and Related Activities [Abstract]
Schedule of Reconciliation of Restructuring Liabilities	A reconciliation of the beginning and ending restructuring liabilities, which is included in accrued wages and benefits and accounts payable in the Condensed Consolidated Balance Sheets as of September 30, 2024, and December 31, 2023, is as follows: Three Months Ended Nine Months Ended (In thousands) September 30, 2024 September 30, 2024 Balance at beginning of period $ 18,657 $ 8,309 Plus: Amounts charged to cost and expense 5,936 36,441 Less: Amounts paid ( 7,770 ) ( 27,927 ) Balance as of September 30, 2024 $ 16,823 $ 16,823 For the Year Ended (In thousands) December 31, 2023 Balance as of December 31, 2022 $ 159 Plus: Amounts charged to cost and expense 22,241 Less: Amounts paid ( 14,091 ) Balance as of December 31, 2023 $ 8,309
Schedule of Components of Restructuring Expenses	Restructuring expenses included in the Condensed Consolidated Statements of Loss are for the three and nine months ended September 30, 2024 and 2023: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 Network Solutions - Cost of revenue $ 517 $ 611 $ 3,359 $ 669 Network Solutions - other (credits), charges ( 328 ) 21,043 $ 8,597 21,043 Services & Support - Cost of revenue ( 182 ) ( 24 ) 2,086 ( 6 ) Cost of revenue $ 7 $ 21,630 $ 14,042 $ 21,706 Selling, general and administrative expenses 2,681 3,387 7,980 6,960 Research and development expenses 3,248 ( 144 ) 18,554 4,512 Total restructuring expenses $ 5,936 $ 24,873 $ 40,576 $ 33,178 The following table represents the components of restructuring expenses by geographic area for the three and nine months ended September 30, 2024 and 2023: Three Months Ended Nine Months Ended September 30, September 30, (In thousands) 2024 2023 2024 2023 United States $ 1,208 $ 22,598 $ 17,495 $ 25,217 International 4,728 2,275 23,081 7,961 Total restructuring expenses $ 5,936 $ 24,873 $ 40,576 $ 33,178

Summary of Significant Accoun_4

Summary of Significant Accounting Policies - Additional Information (Detail) $ / shares in Units, $ in Thousands	3 Months Ended										6 Months Ended		9 Months Ended						12 Months Ended
	Sep. 30, 2024 USD ($) shares		Jun. 30, 2024 USD ($) $ / shares	Mar. 31, 2024 USD ($) $ / shares	Dec. 31, 2023 USD ($) $ / shares	Sep. 30, 2023 USD ($) $ / shares shares		Sep. 30, 2023 EUR (€) shares	Jun. 30, 2023 USD ($) $ / shares	Mar. 31, 2023 USD ($) $ / shares	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) shares		Sep. 30, 2024 EUR (€) shares	Sep. 30, 2023 USD ($) shares		Sep. 30, 2023 EUR (€) shares	Dec. 31, 2023 USD ($)	Sep. 30, 2024 EUR (€)	Oct. 18, 2022 shares
Summary Of Significant Accounting Policy [Line Items]
Percentage of guaranteed interest rate	5%												5%							5%
Percentage of guaranteed interest rate plus a variable component	3.37%												3.37%							3.37%
Aggregate exit compensation payments obligation including guaranteed interest	$ 364,100												$ 364,100							€ 326,900,000
Expire date of exit compensation													Mar. 16, 2023		Mar. 16, 2023
Annual recurring compensation obligation													$ 10,000		€ 8,900,000
Accrued annual recurring compensation obligation	$ 2,400					$ 2,600							$ 7,400			$ 7,600
Annual recurring compensation paid																			$ 10,100
Number of shares tendered | shares	830,000												831,000		831,000	64,000		64,000
Exit compensation payments						9		€ 8,000					$ 17,400		€ 15,700,000	$ 1,200		€ 1,100
Cash and cash equivalents	$ 88,456				$ 87,167								88,456						87,167
Less: Net Income attributable to non-controlling interest	2,382	[1]	$ 2,504	$ 2,531		2,561	[1]		$ 2,534	$ (715)	$ 5,035	$ 1,819	$ 7,417	[1]		4,380	[1]		6,946
Revision [Member]
Summary Of Significant Accounting Policy [Line Items]
Less: Net Income attributable to non-controlling interest			(350)	(349)		(353)			(348)	(345)	(699)	(693)				(1,046)			(1,399)
Previously Reported [Member]
Summary Of Significant Accounting Policy [Line Items]
Less: Net Income attributable to non-controlling interest			$ 2,854	$ 2,880		$ 2,914			$ 2,882	$ (370)	$ 5,734	$ 2,512				$ 5,426			$ 8,345
Wells Fargo Credit Agreement [Member]
Summary Of Significant Accounting Policy [Line Items]
Net leverage ratio													0.0325		0.0325
Wells Fargo Credit Agreement [Member] | First Quarter Ending Springing Covenant Period [Member]
Summary Of Significant Accounting Policy [Line Items]
Net leverage ratio													0.04		0.04
Wells Fargo Credit Agreement [Member] | Third And Fourth Quarters Ending Springing Covenant Event [Member]
Summary Of Significant Accounting Policy [Line Items]
Net leverage ratio													0.035		0.035
Wells Fargo Credit Agreement [Member] | Acorn HoldCo, Inc., [Member]
Summary Of Significant Accounting Policy [Line Items]
Available for future borrowings	205,600												$ 205,600
Credit agreement current borrowing capacity	$ 24,100												$ 24,100
Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Number of shares tendered | shares						1,000		1,000
Maximum [Member] | Wells Fargo Credit Agreement [Member]
Summary Of Significant Accounting Policy [Line Items]
Net leverage ratio					0.05								0.05		0.05
Maximum [Member] | Wells Fargo Credit Agreement [Member] | First Quarter Ending Springing Covenant Period [Member]
Summary Of Significant Accounting Policy [Line Items]
Net leverage ratio													0.04		0.04
Minimum [Member] | Wells Fargo Credit Agreement [Member]
Summary Of Significant Accounting Policy [Line Items]
Net leverage ratio													0.035		0.035
Fixed charge coverage ratio					0.0125								0.0125		0.0125
Minimum [Member] | Wells Fargo Credit Agreement [Member] | Third And Fourth Quarters Ending Springing Covenant Event [Member]
Summary Of Significant Accounting Policy [Line Items]
Net leverage ratio													0.035		0.035
Adtran Networks [Member]
Summary Of Significant Accounting Policy [Line Items]
Annual recurring compensation payment per share | $ / shares			$ 0.52	$ 0.52	$ 0.52	$ 0.52			$ 0.52	$ 0.52
Accrued liability per share | $ / shares			$ 0.59	$ 0.59	$ 0.59	$ 0.59			$ 0.59	$ 0.59
Number of shares tendered | shares	830,000												831,000		831,000	64,000		64,000
Exit compensation payments						$ 9,000		€ 15,700,000					$ 17,400		€ 8,000	$ 1,200		€ 1,100,000
Equity ownership percentage	33%				34.60%								33%						34.60%	33%
Adtran Networks [Member] | Maximum [Member]
Summary Of Significant Accounting Policy [Line Items]
Number of additional shares authorized to purchase | shares																					15,346,544
Number of shares tendered | shares						1,000		1,000
[1] For the three and nine months ended September 30, 2024, we accrued $ 2.4 million and $ 7.4 million, respectively, net income attributable to non-controlling interest, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA. For the three and nine months ended September 30, 2023, we accrued $ 2.6 million and $ 7.6 million, respectively, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA, partially offset by a $ 3.2 million net loss attributable to non-controlling interests pre-DPLTA for the nine months ended September 30, 2023.

Summary of Significant Accoun_5

Summary of Significant Accounting Policies - Summary of Impact of Revision to Specific Line Items in Condensed Consolidated Balance Sheets, Condensed Consolidated Statements of Loss, and Condensed Consolidated Statements of Comprehensive Loss (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								6 Months Ended		9 Months Ended				12 Months Ended
	Sep. 30, 2024		Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023		Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024		Sep. 30, 2023		Dec. 31, 2023	Dec. 31, 2022
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accrued Expenses and Other Liabilities	$ 34,482		$ 34,904	$ 35,001	$ 16,359		$ 15,706	$ 15,640	$ 34,904	$ 15,706	$ 34,482		$ 16,359		$ 36,204
Redeemable Non-Controlling Interest	421,776		442,122	442,146	442,212		442,218	442,238	442,122	442,218	421,776		442,212		442,152
Accumulated Other Comprehensive Income	47,377		28,280	29,661	12,078		41,485	34,527	28,280	41,485	47,377		12,078		47,465
Retained Earnings	(635,164)		(606,656)	(557,126)	(122,534)		(37,073)	8,781	(606,656)	(37,073)	(635,164)		(122,534)		(232,905)
Total Equity	213,994		219,954	267,025	675,651		786,409	820,938	219,954	786,409	213,994		675,651		604,829	$ 1,303,613
Total Liabilities, Redeemable Non-Controlling Interest and Equity	1,273,146		1,290,782	1,327,906	1,742,169		1,882,938	1,938,595	1,290,782	1,882,938	1,273,146		1,742,169		1,682,512
Less: Net Income (Loss) attributable to non-controlling interest	2,382	[1]	2,504	2,531	2,561	[1]	2,534	(715)	5,035	1,819	7,417	[1]	4,380	[1]	6,946
Net Income (Loss)	$ (31,239)		$ (49,515)	$ (324,201)	$ (78,210)		$ (38,749)	$ (39,738)	$ (373,716)	$ (78,487)	$ (404,955)		$ (156,697)		$ (266,289)
Loss per common share attributable to ADTRAN Holdings, Inc. - basic	$ (0.36)	[2]	$ (0.63)	$ (4.12)	$ (1)		$ (0.5)	$ (0.51)	$ (4.74)	$ (1)	$ (5.1)	[2]	$ (2)		$ (3.39)
Loss per common share attributable to ADTRAN Holdings, Inc. - diluted	$ (0.36)	[2]	$ (0.63)	$ (4.12)	$ (1)		$ (0.5)	$ (0.51)	$ (4.74)	$ (1)	$ (5.1)	[2]	$ (2)		$ (3.39)
Foreign currency translation gain (loss)	$ 18,988		$ (1,374)	$ (17,744)	$ (29,715)		$ 6,941	$ 8,679	$ (19,118)	$ 15,620	$ (130)		$ (14,095)		$ 22,757
Other Comprehensive Income (Loss), net of tax	19,097		(1,381)	(17,804)	(29,407)		6,958	8,783	(19,185)	15,741	(88)		(13,666)		21,721
Comprehensive Loss, net of tax	(9,760)		(48,392)	(339,474)	(105,056)		(29,257)	(31,670)	(387,866)	(60,927)	(397,626)		(165,983)		(237,622)
Less: Comprehensive Income attributable to non-controlling interest, net of tax	2,382		2,504	2,531	2,561		2,534	(333)	5,035	2,201	7,417		4,762		7,328
Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax	$ (12,142)		(50,896)	(342,005)	(107,617)		(31,791)	(31,337)	(392,901)	(63,128)	$ (405,043)		(170,745)		(244,950)
As Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accrued Expenses and Other Liabilities			36,307	36,404	17,408		16,401	15,986	36,307	16,401			17,408		37,607
Redeemable Non-Controlling Interest			439,743	441,635	431,921		445,462	442,668	439,743	445,462			431,921		451,756
Accumulated Other Comprehensive Income			28,274	29,656	12,075		41,483	34,526	28,274	41,483			12,075		47,461
Retained Earnings			(606,375)	(558,363)	(113,289)		(41,010)	8,006	(606,375)	(41,010)			(113,289)		(243,908)
Total Equity			220,229	265,783	684,893		782,470	820,162	220,229	782,470			684,893		593,822
Total Liabilities, Redeemable Non-Controlling Interest and Equity			1,290,782	1,327,906	1,742,169		1,882,938	1,938,595	1,290,782	1,882,938			1,742,169		1,682,512
Less: Net Income (Loss) attributable to non-controlling interest			2,854	2,880	2,914		2,882	(370)	5,734	2,512			5,426		8,345
Net Income (Loss)			$ (49,865)	$ (324,550)	$ (78,563)		$ (39,097)	$ (40,083)	$ (374,415)	$ (79,180)			$ (157,743)		$ (267,688)
Loss per common share attributable to ADTRAN Holdings, Inc. - basic			$ (0.63)	$ (4.12)	$ (1)		$ (0.5)	$ (0.51)	$ (4.75)	$ (1.01)			$ (2.01)		$ (3.41)
Loss per common share attributable to ADTRAN Holdings, Inc. - diluted			$ (0.63)	$ (4.12)	$ (1)		$ (0.5)	$ (0.51)	$ (4.75)	$ (1.01)			$ (2.01)		$ (3.41)
Foreign currency translation gain (loss)			$ (1,375)	$ (17,745)	$ (29,716)		$ 6,940	$ 8,678	$ (19,120)	$ 15,618			$ (14,098)		$ 22,753
Other Comprehensive Income (Loss), net of tax			(1,382)	(17,805)	(29,408)		6,957	8,782	(19,187)	15,739			(13,669)		21,717
Comprehensive Loss, net of tax			(48,393)	(339,475)	(105,057)		(29,258)	(31,671)	(387,868)	(60,929)			(165,986)		(237,626)
Less: Comprehensive Income attributable to non-controlling interest, net of tax			2,854	2,880	2,914		2,882	12	5,734	2,894			5,808		8,727
Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax			(51,247)	(342,355)	(107,971)		(32,140)	(31,683)	(393,602)	(63,823)			(171,794)		(246,353)
Revision [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Accrued Expenses and Other Liabilities			(1,403)	(1,403)	(1,049)		(695)	(346)	(1,403)	(695)			(1,049)		(1,403)
Redeemable Non-Controlling Interest			2,379	511	10,291		(3,244)	(430)	2,379	(3,244)			10,291		(9,604)
Accumulated Other Comprehensive Income			6	5	3		2	1	6	2			3		4
Retained Earnings			(281)	1,237	(9,245)		3,937	775	(281)	3,937			(9,245)		11,003
Total Equity			(275)	1,242	(9,242)		3,939	776	(275)	3,939			(9,242)		11,007
Less: Net Income (Loss) attributable to non-controlling interest			(350)	(349)	(353)		(348)	(345)	(699)	(693)			(1,046)		(1,399)
Net Income (Loss)			350	349	353		348	345	$ 699	$ 693			$ 1,046		$ 1,399
Loss per common share attributable to ADTRAN Holdings, Inc. - basic									$ 0.01	$ 0.01			$ 0.01		$ 0.02
Loss per common share attributable to ADTRAN Holdings, Inc. - diluted									$ 0.01	$ 0.01			$ 0.01		$ 0.02
Foreign currency translation gain (loss)			1	1	1		1	1	$ 2	$ 2			$ 3		$ 4
Other Comprehensive Income (Loss), net of tax			1	1	1		1	1	2	2			3		4
Comprehensive Loss, net of tax			1	1	1		1	1	2	2			3		4
Less: Comprehensive Income attributable to non-controlling interest, net of tax			(350)	(349)	(353)		(348)	(345)	(699)	(693)			(1,046)		(1,399)
Comprehensive Loss attributable to ADTRAN Holdings, Inc., net of tax			$ 351	$ 350	$ 354		$ 349	$ 346	$ 701	$ 695			$ 1,049		$ 1,403
[1] For the three and nine months ended September 30, 2024, we accrued $ 2.4 million and $ 7.4 million, respectively, net income attributable to non-controlling interest, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA. For the three and nine months ended September 30, 2023, we accrued $ 2.6 million and $ 7.6 million, respectively, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA, partially offset by a $ 3.2 million net loss attributable to non-controlling interests pre-DPLTA for the nine months ended September 30, 2023. Loss per common share attributable to ADTRAN Holdings, Inc. - basic and diluted - reflects a $ 3.0 million effect of redemption of RNCI for the three and nine months ended September 30, 2024. See Note 15 for additional information.

Summary of Significant Accoun_6

Summary of Significant Accounting Policies - Summary of Impact of Revision to Specific Line Items in Condensed Consolidated Statements of Changes in Stockholders (Details) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning Balance	$ 219,954	$ 267,025	$ 604,829	$ 786,409	$ 820,938	$ 1,303,613	$ 604,829	$ 1,303,613	$ 604,829	$ 1,303,613	$ 1,303,613
Other Comprehensive Income (Loss), net of tax	19,097	(1,381)	(17,804)	(29,407)	6,958	8,783	(19,185)	15,741	(88)	(13,666)	21,721
Ending Balance	213,994	219,954	267,025	675,651	786,409	820,938	219,954	786,409	213,994	675,651	604,829
Retained Earnings (Deficit) [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning Balance	(606,656)	(557,126)	(232,905)	(37,073)	8,781	55,338	(232,905)	55,338	(232,905)	55,338	55,338
Annual recurring compensation earned		(2,504)	(2,531)	(2,561)	(2,534)	(2,464)					(10,125)
Ending Balance	(635,164)	(606,656)	(557,126)	(122,534)	(37,073)	8,781	(606,656)	(37,073)	(635,164)	(122,534)	(232,905)
Accumulated Other Comprehensive Income [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning Balance	28,280	29,661	47,465	41,485	34,527	26,126	47,465	26,126	47,465	26,126	26,126
Other Comprehensive Income (Loss), net of tax	19,097	(1,381)	(17,804)	(29,407)	6,958	8,401					21,339
Ending Balance	47,377	28,280	29,661	12,078	41,485	34,527	28,280	41,485	47,377	12,078	47,465
As Previously Reported [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning Balance	220,229	265,783	593,822	782,470	820,162		593,822		593,822
Other Comprehensive Income (Loss), net of tax		(1,382)	(17,805)	(29,408)	6,957	8,782	(19,187)	15,739		(13,669)	21,717
Ending Balance		220,229	265,783	684,893	782,470	820,162	220,229	782,470		684,893	593,822
As Previously Reported [Member] | Retained Earnings (Deficit) [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning Balance	(606,375)	(558,363)	(243,908)	(41,010)	8,006		(243,908)		(243,908)
Annual recurring compensation earned		(2,854)	(2,880)	(2,914)	(2,882)	(2,809)					(11,524)
Foreign currency remeasurement of redeemable non-controlling interest		1,868	10,115	13,535	(2,814)	(430)					(9,604)
Ending Balance		(606,375)	(558,363)	(113,289)	(41,010)	8,006	(606,375)	(41,010)		(113,289)	(243,908)
As Previously Reported [Member] | Accumulated Other Comprehensive Income [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning Balance	28,274	29,656	47,461	41,483	34,526		47,461		47,461
Other Comprehensive Income (Loss), net of tax		(1,382)	(17,805)	(29,408)	6,957	8,400					21,335
Ending Balance		28,274	29,656	12,075	41,483	34,526	28,274	41,483		12,075	47,461
Revision [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning Balance	(275)	1,242	11,007	3,939	776		11,007		11,007
Other Comprehensive Income (Loss), net of tax		1	1	1	1	1	2	2		3	4
Ending Balance		(275)	1,242	(9,242)	3,939	776	(275)	3,939		(9,242)	11,007
Revision [Member] | Retained Earnings (Deficit) [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning Balance	(281)	1,237	11,003	3,937	775		11,003		11,003
Annual recurring compensation earned		350	349	353	348	345					1,399
Foreign currency remeasurement of redeemable non-controlling interest		(1,868)	(10,115)	(13,535)	2,814	430					9,604
Ending Balance		(281)	1,237	(9,245)	3,937	775	(281)	3,937		(9,245)	11,003
Revision [Member] | Accumulated Other Comprehensive Income [Member]
Error Corrections and Prior Period Adjustments Restatement [Line Items]
Beginning Balance	$ 6	5	4	2	1		4		$ 4
Other Comprehensive Income (Loss), net of tax		1	1	1	1	1					4
Ending Balance		$ 6	$ 5	$ 3	$ 2	$ 1	$ 6	$ 2		$ 3	$ 4

Revenue - Additional Informatio

Revenue - Additional Information (Detail)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) Category	Sep. 30, 2023 USD ($)	Dec. 31, 2022 USD ($)	Jul. 01, 2024 USD ($)	Dec. 31, 2023 USD ($)	Dec. 19, 2023 USD ($)
Revenue [Line Items]
Number of categories | Category			3
Accounts receivable, allowance for credit losses	$ 420,000		$ 420,000				$ 400,000
Allowance for credit losses related to contract assets	0	$ 0	0	$ 0
Recognized revenue	10,030,000	6,100,000	43,100,000	31,300,000	$ 60,400,000
Factor [Member] | Purchase Agreement [Member]
Revenue [Line Items]
Accounts receivable	16,700,000		16,700,000
Secured revolving credit facility amount						$ 40,000,000
Factor [Member] | Purchase Agreement [Member] | Interest expense [Member]
Revenue [Line Items]
Cost of receivables	300,000	$ 300,000	300,000	$ 900,000
Factor [Member] | Purchase Agreement [Member] | Other Assets [Member]
Revenue [Line Items]
Accounts receivable gross	3,700,000		3,700,000
Prior Factoring Agreement [Member] | Purchase Agreement [Member]
Revenue [Line Items]
Secured revolving credit facility amount								$ 40,000,000
Secured borrowings current borrowing capacity							14,300,000
Secured borrowings, available for future borrowings							25,400,000
Secured borrowings, account receivable pledged as collateral							$ 16,800,000
Secured borrowings, fee expense incurred			600,000
Contractual Maintenance Agreements, Contractual SaaS and Subscription Services and Hardware Orders [Member]
Revenue [Line Items]
Remaining performance obligations	$ 280,800,000		$ 280,800,000

Revenue - Additional Informat_2

Revenue - Additional Information (Detail1) - Revenue, Remaining Performance Obligation, Expected Timing of Satisfaction, Start Date: 2024-10-01	Sep. 30, 2024
Revenue [Line Items]
Remaining performance obligations, percentage	66%
Remaining performance obligations, period	12 months

Revenue - Disaggregate of Reven

Revenue - Disaggregate of Revenue by Reportable Segment and Revenue Category (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation Of Revenue [Line Items]
Revenue	$ 227,704	$ 272,331	$ 679,868	$ 923,621
Subscriber Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	90,096	61,485	242,262	222,486
Optical Networking Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	70,535	116,200	219,314	406,952
Access & Aggregation Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	67,073	94,646	218,292	294,183
Network Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	181,488	228,564	541,955	793,984
Network Solutions [Member] | Subscriber Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	81,060	52,921	215,044	196,726
Network Solutions [Member] | Optical Networking Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	47,474	94,592	152,068	342,390
Network Solutions [Member] | Access & Aggregation Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	52,954	81,051	174,843	254,868
Services & Support [Member]
Disaggregation Of Revenue [Line Items]
Revenue	46,216	43,767	137,913	129,637
Services & Support [Member] | Subscriber Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	9,036	8,564	27,218	25,760
Services & Support [Member] | Optical Networking Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	23,061	21,608	67,246	64,562
Services & Support [Member] | Access & Aggregation Solutions [Member]
Disaggregation Of Revenue [Line Items]
Revenue	$ 14,119	$ 13,595	$ 43,449	$ 39,315

Revenue - Information about Rec

Revenue - Information about Receivable, Contract Assets, and Unearned Revenue from Contracts with Customers (Detail) - USD ($) $ in Thousands		Sep. 30, 2024	Dec. 31, 2023
Revenue from Contract with Customer [Abstract]
Accounts receivable, net		$ 172,025	$ 216,445
Contract assets	[1]	668	691
Unearned revenue		54,615	46,731
Non-current unearned revenue		$ 24,901	$ 25,109
[1] Included in other receivables on the Condensed Consolidated Balance Sheets.

Income Taxes - Additional Infor

Income Taxes - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Income Tax Disclosure [Line Items]
Effective tax rate expense (benefit)	1.40%	(18.00%)	(3.90%)	(19.20%)
Deferred tax assets	$ 91.3		$ 91.3
Valuation allowance established against deferred tax assets	$ 87.1		$ 87.1

Stock-Based Compensation (Stock

Stock-Based Compensation (Stock Incentive Plans and Stock Options) - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock-based compensation expense	$ 3,600	$ 4,200	$ 11,400	$ 12,200
Shares available for issuance	4,700,000		4,700,000
Aggregate intrinsic value based on fair market value	$ 829		$ 829		$ 3,087
Total pre-tax intrinsic value of options exercised	$ 34		$ 200
Stock options vested	100,000	0	100,000	0
2024 Employee Stock Incentive Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share available issuance under shareholder	4,000,000		4,000,000
Contractual term			10 years
Multiplier used when issuing PSUs, restricted stock and RSUs	1		1
Forfeiture of stock increase in issuance of common stock	1		1
2024 Employee Stock Incentive Plan [Member] | RSUs [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period			4 years
2024 Employee Stock Incentive Plan [Member] | Employee Stock Option
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Vesting period			4 years
2024 Directors Stock Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Share available issuance under shareholder	700,000		700,000
Contractual term			10 years
Multiplier used when issuing PSUs, restricted stock and RSUs	1		1
Forfeiture of stock increase in issuance of common stock	1		1
2020 Employee Stock Incentive Plan [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Number of additional shares of common stock granted			0
Adtran Networks SE [Member]
Share-Based Compensation Arrangement by Share-Based Payment Award [Line Items]
Stock options vested			0
Liability based award cash settled	$ 200

Stock-Based Compensation - Stoc

Stock-Based Compensation - Stock-Based Compensation Expense Related to Stock Options, PSUs, RSUs and Restricted Stock (Detail) shares in Thousands	9 Months Ended
	Sep. 30, 2024 $ / shares shares
Share-Based Payment Arrangement [Abstract]
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, beginning balance | shares	1,942
Number of Shares, PSUs, RSUs and restricted stock granted | shares	1,097
Number of Shares, PSUs, RSUs and restricted stock vested | shares	(263)
Number of Shares, PSUs, RSUs and restricted stock forfeited | shares	(111)
Number of Shares, Unvested PSUs, RSUs and restricted stock outstanding, ending balance | shares	2,665
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Beginning Balance | $ / shares	$ 17.46
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock granted | $ / shares	7.85
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock vested | $ / shares	18.86
Weighted Avg. Grant Date Fair Value, PSUs, RSUs and restricted stock forfeited | $ / shares	14.25
Weighted Avg. Grant Date Fair Value, Unvested PSUs, RSUs and restricted stock outstanding, Ending Balance | $ / shares	$ 13.5

Stock-Based Compensation (PSUs,

Stock-Based Compensation (PSUs, RSUs and Restricted Stock) - Additional Information (Detail) $ in Millions	9 Months Ended
	Sep. 30, 2024 USD ($)
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	$ 13.3
Recognition period of unvested compensation expense	2 years 2 months 12 days
Performance Stock Units (PSUs) [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 11
Recognition period of unvested compensation expense	1 year 3 months 18 days
Time-Based RSUs [Member]
Share Based Compensation Arrangement By Share Based Payment Award [Line Items]
Unrecognized compensation expense related to stock options	$ 4.2
Recognition period of unvested compensation expense	1 year 2 months 12 days

Stock-Based Compensation - Summ

Stock-Based Compensation - Summary of Stock Options Outstanding (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Share-Based Payment Arrangement [Abstract]
Number of Stock Options, Stock options outstanding, Beginning Balance	3,894
Number of Stock Options, Stock options exercised	(36)
Number of Stock Options, Stock options forfeited	(171)
Number of Stock Options, Stock options expired	(243)
Number of Stock Options, Stock options outstanding, Ending Balance	3,444	3,894
Number of Stock Options, Stock options exercisable	1,342
Weighted Avg. Exercise Price, Stock options outstanding, Beginning Balance	$ 10.32
Weighted Avg. Exercise Price, Stock options exercised	6.06
Weighted Avg. Exercise Price, Stock options forfeited	6.68
Weighted Avg. Exercise Price, Stock options expired	9.31
Weighted Avg. Exercise Price, Stock options outstanding, Ending Balance	10.61	$ 10.32
Weighted Avg. Exercise Price, Stock options exercisable	$ 12.63
Weighted Avg. Remaining Contractual Life In Years, Stock options outstanding	4 years 7 months 20 days	5 years 3 months
Weighted Avg. Remaining Contractual Life in Years, Stock options exercisable	1 year 1 month 9 days
Aggregate Intrinsic Value, Stock options outstanding	$ 829	$ 3,087

Investments - Gross Realized Ga

Investments - Gross Realized Gains and Losses on Sale of Debt Securities (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended
	Sep. 30, 2023	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Gross realized gain on debt securities	$ 5	$ 9
Gross realized loss on debt securities	(317)	(355)
Total loss recognized, net	$ (312)	$ (346)

Investments - Additional Inform

Investments - Additional Information (Detail)	Sep. 30, 2024 USD ($)
Schedule of Investments [Line Items]
Available-for-sale debt securities	$ 0
Other investments	$ 0

Investments - Realized and Unre

Investments - Realized and Unrealized Gains and Losses related to Marketable Equity Securities (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Investments, Debt and Equity Securities [Abstract]
Unrealized gain (loss) on equity securities held	$ 1,372	$ (1,130)	$ 4,371	$ 1,404
Realized (loss) gain on equity securities sold	10	(1)	136	13
Total gain (loss) recognized, net	$ 1,382	$ (1,131)	$ 4,507	$ 1,417

Investments - Cash Equivalents

Investments - Cash Equivalents and Investments held at Fair Value (Detail) - Fair Value, Measurements [Member] - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Schedule of Available-for-sale Securities [Line Items]
Total	$ 37,006	$ 33,045
Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Total	37,006	33,045
Money Market Funds [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	5,500	5,302
Money Market Funds [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Cash equivalents	5,500	5,302
Marketable Equity Securities - Various Industries [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	1,035	905
Marketable Equity Securities - Various Industries [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	1,035	905
Deferred Compensation Plan Assets [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	30,471	26,838
Deferred Compensation Plan Assets [Member] | Quoted Prices in Active Market for Identical Assets (Level 1) [Member]
Schedule of Available-for-sale Securities [Line Items]
Marketable equity securities	$ 30,471	$ 26,838

Inventory - Components of Inven

Inventory - Components of Inventory (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Inventory Disclosure [Abstract]
Raw materials	$ 114,873	$ 152,140
Work in process	10,942	17,239
Finished goods	157,111	192,916
Total Inventory, net	$ 282,926	$ 362,295

Inventory - Additional Informat

Inventory - Additional Information (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Inventory [Line Items]
Inventory renegotiated charges			$ (69,412)	$ (536)
Inventory write down			4,135	$ 21,043
Business Efficiency Program
Inventory [Line Items]
Inventory renegotiated charges	$ 300		300
Strategy shift charges	$ (300)		8,600
Inventory write down		$ 21,000	4,100
Other charges			$ 4,500

Property, Plant and Equipment -

Property, Plant and Equipment - Property, Plant and Equipment (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Property, Plant and Equipment [Abstract]
Engineering and other equipment	$ 187,753	$ 183,336
Building	79,857	79,215
Computer hardware and software	139,006	101,572
Building and land improvements	59,487	58,238
Furniture and fixtures	21,542	21,368
Land	5,248	5,242
Total property, plant and equipment	492,893	448,971
Less: accumulated depreciation	(345,465)	(325,951)
Total property, plant and equipment, net	$ 147,428	$ 123,020

Property, Plant and Equipment_2

Property, Plant and Equipment - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Property, Plant and Equipment [Line Items]
Depreciation expense	$ 8.7	$ 7.4	$ 24.5	$ 22.6

Goodwill - Summary of Changes i

Goodwill - Summary of Changes in Carrying Amount of Goodwill (Detail) $ in Thousands	9 Months Ended
	Sep. 30, 2024 USD ($)
Goodwill [Line Items]
Goodwill, Beginning balance	$ 353,415
Goodwill impairment	(290,528)
Foreign currency translation adjustments	(6,003)
Goodwill, Ending balance	56,884
Network Solutions [Member]
Goodwill [Line Items]
Goodwill, Beginning balance	297,031
Goodwill impairment	(290,528)
Foreign currency translation adjustments	(6,503)
Goodwill, Ending balance	0
Services & Support [Member]
Goodwill [Line Items]
Goodwill, Beginning balance	56,384
Foreign currency translation adjustments	500
Goodwill, Ending balance	$ 56,884

Goodwill - Additional Informati

Goodwill - Additional Information (Details) - USD ($)	3 Months Ended			9 Months Ended
	Sep. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Goodwill [Line Items]
Impairment charges related to goodwill	$ 0		$ 37,874,000	$ 292,583,000	$ 37,874,000
Accumulated goodwill impairment losses	$ 330,500,000			$ 330,500,000
Network Solutions [Member]
Goodwill [Line Items]
Impairment charges related to goodwill		$ 292,600,000
Services & Support [Member]
Goodwill [Line Items]
Impairment charges related to goodwill			$ 37,900,000

Intangible Assets - Summary of

Intangible Assets - Summary of Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Finite Lived Intangible Assets [Line Items]
Gross Carrying Amount	$ 480,581		$ 478,265
Accumulated Amortization	(194,483)		(150,280)
Net Book Value	$ 286,098	$ 286,098	327,985
Developed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	8 years 6 months
Gross Carrying Amount	$ 332,245		329,369
Accumulated Amortization	(91,210)		(61,271)
Net Book Value	$ 241,035		268,098
Customer Relationships [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	10 years 10 months 24 days
Gross Carrying Amount	$ 54,016		54,856
Accumulated Amortization	(18,461)		(15,943)
Net Book Value	$ 35,555		38,913
Trade Names [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	3 years
Gross Carrying Amount	$ 29,955		29,689
Accumulated Amortization	(24,993)		(16,379)
Net Book Value	$ 4,962		13,310
Backlog [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	1 year 7 months 6 days
Gross Carrying Amount	$ 57,905		57,391
Accumulated Amortization	(55,133)		(52,022)
Net Book Value	$ 2,772		5,369
Licensed Technology [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	9 years
Gross Carrying Amount	$ 5,900		5,900
Accumulated Amortization	(4,288)		(3,797)
Net Book Value	$ 1,612		2,103
Licensing Agreements [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	8 years 6 months
Gross Carrying Amount	$ 560		560
Accumulated Amortization	(398)		(368)
Net Book Value	$ 162		192
Patents [Member]
Finite Lived Intangible Assets [Line Items]
Weighted Average Useful Life (in years)	7 years 3 months 18 days
Gross Carrying Amount			500
Accumulated Amortization			$ (500)

Intangible Assets - Additional

Intangible Assets - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Finite-Lived Intangible Assets [Line Items]
Impairment losses of intangible assets	$ 0	$ 0	$ 0	$ 0
Amortization expense	$ 14,700,000	$ 16,500,000	$ 43,700,000	$ 68,800,000

Intangible Assets - Estimated F

Intangible Assets - Estimated Future Amortization Expense Related to Intangible Assets (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023
Finite-Lived Intangible Assets, Net, Amortization Expense, Fiscal Year Maturity [Abstract]
2024	$ 14,905
2025	47,737
2026	44,408
2027	43,018
2028	42,870
Thereafter	93,160
Net Book Value	$ 286,098	$ 286,098	$ 327,985

Hedging - Additional Informatio

Hedging - Additional Information (Detail) € in Millions, $ in Millions	3 Months Ended	9 Months Ended
	Sep. 30, 2024 EUR (€) ForwardContracts	Sep. 30, 2024 EUR (€) ForwardContracts	Mar. 21, 2023 EUR (€)	Mar. 21, 2023 USD ($)
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount, daily fixed forward conversion rate			0.01085	0.01085
Foreign Exchange Forward [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Number of forward rate contracts outstanding | ForwardContracts	41	41
Cross-Currency Swap Arrangement [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	€ 160	€ 160	€ 160
Forward contract tranche settled on hedge	20	20
Cross-Currency Swap Arrangement [Member] | Eight Quarterly Tranches [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	20	20
Cross-Currency Swap Arrangement [Member] | Two Quarterly Tranches [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount	€ 20	€ 20		$ 20
Cross-Currency Swap Arrangement [Member] | Minimum [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount, daily fixed forward conversion rate	0.0098286	0.0098286
Cross-Currency Swap Arrangement [Member] | Maximum [Member]
Derivative Instruments and Hedging Activities Disclosures [Line Items]
Aggregate notional amount, daily fixed forward conversion rate	0.010329	0.010329

Hedging - Schedule of Fair Valu

Hedging - Schedule of Fair Values of Derivative Instruments (Detail) - Derivatives Not Designated as Hedging Instruments [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024	Dec. 31, 2023
Other (expense) income, net
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Foreign exchange contracts	$ (411)	$ 1,012	$ (380)	$ 1,076
Level 2 [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Total derivatives					$ 682	$ 4,848
Level 2 [Member] | Other Receivables [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Foreign exchange contracts - derivative assets					1,712	7,125
Level 2 [Member] | Accounts Payable [Member]
Derivative Instruments Not Designated as Hedging Instruments [Abstract]
Foreign exchange contracts - derivative liabilities					$ (1,030)	$ (2,277)

Credit Agreements - Carrying Am

Credit Agreements - Carrying Amount of Non-Current Revolving Facility (Details) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Line of Credit Facility [Line Items]
Total non-current revolving credit facility	$ 189,849	$ 195,000
Wells Fargo Credit Agreement [Member]
Line of Credit Facility [Line Items]
Total non-current revolving credit facility	$ 189,849	$ 195,000

Credit Agreements - Additional

Credit Agreements - Additional Information (Detail) $ in Thousands						3 Months Ended	9 Months Ended
	Jun. 30, 2025 USD ($)	Dec. 31, 2024 USD ($)	Jun. 04, 2024 USD ($)	Aug. 09, 2023 USD ($)	Jul. 18, 2022 USD ($)	Dec. 31, 2023 USD ($)	Sep. 30, 2024 USD ($)
Line Of Credit Facility [Line Items]
Weighted average interest rate							8.45%
Revolving line of credit						$ 195,000	$ 189,849
Debt instrument default interest rate percentage							2%
Daily Simple SOFR [Member]
Line Of Credit Facility [Line Items]
Credit facility, floor rate							0%
Applicable margin rate							3.15%
Base Rate [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							2.15%
EURIBOR [Member]
Line Of Credit Facility [Line Items]
Credit facility, floor rate							0%
Applicable margin rate							3.25%
Maximum [Member] | Daily Simple SOFR [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							2.65%
Maximum [Member] | Base Rate [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							1.65%
Maximum [Member] | EURIBOR [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							2.75%
Minimum [Member] | Daily Simple SOFR [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							1.65%
Minimum [Member] | Base Rate [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							0.65%
Minimum [Member] | EURIBOR [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							1.75%
Wells Fargo Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Revolving line of credit						$ 195,000	$ 189,849
Commitment fee percentage							0.25%
Net leverage ratio							0.0325
Wells Fargo Credit Agreement [Member] | Daily Simple SOFR [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							0.10%
Wells Fargo Credit Agreement [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Commitment fee percentage							0.25%
Net leverage ratio						0.05	0.05
Wells Fargo Credit Agreement [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Commitment fee percentage							0.20%
Net leverage ratio							0.035
Fixed charge coverage ratio						0.0125	0.0125
Wells Fargo Credit Agreement [Member] | Federal Reserve Bank Advances [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							1%
Wells Fargo Credit Agreement [Member] | Federal Reserve Bank Advances [Member] | Daily Simple SOFR [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							1%
Wells Fargo Credit Agreement [Member] | Federal Reserve Bank Advances [Member] | Base Rate [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate							1%
Wells Fargo Credit Agreement Amendment [Member]
Line Of Credit Facility [Line Items]
Secured revolving credit facility amount							$ 50,000
Aggregate principal amount				$ 172,500
Wells Fargo Credit Agreement Amendment [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Revolving line of credit							300,000
Wells Fargo Credit Agreement Amendment [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Aggregate principal amount							75,000
Wells Fargo Credit Agreement Amendment [Member] | Delayed Draw Term Loan [Member]
Line Of Credit Facility [Line Items]
Revolving line of credit				$ 50,000
Percentage available for borrowing				60%
Acorn HoldCo, Inc., [Member] | Wells Fargo Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Secured revolving credit facility amount				$ 400,000	$ 400,000		400,000
Revolving line of credit							189,800
Credit facility, average outstanding amount							4,400
Letters of credit may be utilize							50,000
Available for future borrowings							205,600
Credit agreement current borrowing capacity							24,100
Acorn HoldCo, Inc., [Member] | Wells Fargo Credit Agreement Amendment [Member]
Line Of Credit Facility [Line Items]
Secured revolving credit facility amount			$ 400,000
Acorn HoldCo, Inc., [Member] | Wells Fargo Credit Agreement - Subline [Member]
Line Of Credit Facility [Line Items]
Revolving line of credit							75,000
Threshold prepayments of outstanding loans german commitment reduction amount			75,000
Credit facility, average outstanding amount			$ 100,000	$ 100,000	$ 100,000
Acorn HoldCo, Inc., [Member] | Wells Fargo Credit Agreement - US Borrower [Member]
Line Of Credit Facility [Line Items]
Revolving line of credit							$ 115,000
Scenario Forecast [Member] | EURIBOR [Member]
Line Of Credit Facility [Line Items]
Applicable margin rate	1%	1%
Scenario Forecast [Member] | Wells Fargo Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Secured revolving credit facility amount	$ 300,000	$ 340,000
First Quarter Ending Springing Covenant Period [Member] | Wells Fargo Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Net leverage ratio							0.04
First Quarter Ending Springing Covenant Period [Member] | Wells Fargo Credit Agreement [Member] | Maximum [Member]
Line Of Credit Facility [Line Items]
Net leverage ratio							0.04
Second Quarter Ending Springing Covenant Event [Member] | Wells Fargo Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Net leverage ratio							0.0375
Third and Fourth Quarters Ending Springing Covenant Event [Member] | Wells Fargo Credit Agreement [Member]
Line Of Credit Facility [Line Items]
Net leverage ratio							0.035
Third and Fourth Quarters Ending Springing Covenant Event [Member] | Wells Fargo Credit Agreement [Member] | Minimum [Member]
Line Of Credit Facility [Line Items]
Net leverage ratio							0.035

Credit Agreements - Additiona_2

Credit Agreements - Additional Information (Detail1) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Line of Credit Facility [Line Items]
Cash and cash equivalents	$ 88,456	$ 87,167
Wells Fargo Credit Agreement Amendment [Member] | Credit Parties [Member]
Line of Credit Facility [Line Items]
Cash and cash equivalents	50,000	50,000
Wells Fargo Credit Agreement Amendment [Member] | Company and Subsidiaries [Member]
Line of Credit Facility [Line Items]
Cash and cash equivalents	$ 70,000	$ 70,000

Employee Benefit Plans - Additi

Employee Benefit Plans - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Defined Benefit Plan Disclosure [Line Items]
Non-current pension liability	$ 12,149		$ 12,543
Current pension liability	100		$ 100
Contributions to defined benefit pension plans	3,000	$ 2,800
Defined benefit pension plans for the remainder of fiscal year	$ 1,000

Employee Benefit Plans - Schedu

Employee Benefit Plans - Schedule of the Components of Net Periodic Pension Cost (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Defined Benefit Plan, Net Periodic Benefit Cost (Credit) [Abstract]
Service cost	$ 340	$ 401	$ 1,013	$ 1,203
Interest cost	$ 286	$ (33)	$ 852	$ (99)
Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Interest Cost, Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)
Expected return on plan assets	$ (360)	$ 59	$ (1,074)	$ 177
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Expected Return (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)
Amortization of actuarial losses	$ 2	$ 7	$ 7	$ 20
Defined Benefit Plan, Net Periodic Benefit (Cost) Credit, Amortization of Gain (Loss), Statement of Income or Comprehensive Income [Extensible Enumeration]	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)	Other Nonoperating Income (Expense)
Net periodic benefit cost	$ 268	$ 434	$ 798	$ 1,301

Equity - Changes in Accumulated

Equity - Changes in Accumulated Other Comprehensive Income, Net of Tax, by Component (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	$ 219,954	$ 786,409	$ 604,829	$ 1,303,613
Other comprehensive (loss) income before reclassifications	18,978	(29,080)	(264)	(13,362)
Amounts reclassified from accumulated other comprehensive income	119	(327)	176	(304)
Net current period other comprehensive (loss) income	19,097	(29,407)	(88)	(13,666)
Less: Comprehensive income (loss) attributable to non-controlling interest, net of tax				382
Ending Balance	213,994	675,651	213,994	675,651
ASU 2018-02 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	385	385	385	385
Ending Balance	385	385	385	385
Accumulated Other Comprehensive Income (Loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	28,280	41,485	47,465	26,126
Ending Balance	47,377	12,078	47,377	12,078
Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(382)	(773)	(382)	(836)
Other comprehensive (loss) income before reclassifications	(10)	635	(134)	733
Amounts reclassified from accumulated other comprehensive income	10	(244)	134	(279)
Net current period other comprehensive (loss) income		391		454
Ending Balance	(382)	(382)	(382)	(382)
Defined Benefit Plan Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	(2,573)	(958)	(2,506)	(1,016)
Amounts reclassified from accumulated other comprehensive income	109	(83)	42	(25)
Net current period other comprehensive (loss) income	109	(83)	42	(25)
Ending Balance	(2,464)	(1,041)	(2,464)	(1,041)
Foreign Currency Adjustments [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Beginning Balance	30,850	42,831	49,968	27,593
Other comprehensive (loss) income before reclassifications	18,988	(29,715)	(130)	(14,095)
Net current period other comprehensive (loss) income	18,988	(29,715)	(130)	(14,095)
Less: Comprehensive income (loss) attributable to non-controlling interest, net of tax				382
Ending Balance	$ 49,838	$ 13,116	$ 49,838	$ 13,116

Equity - Reclassifications Out

Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Loss Before Income Taxes	$ (28,467)			$ (92,202)					$ (413,659)	$ (188,546)
Tax (expense) benefit	(390)			16,553					16,121	36,229
Net Loss attributable to ADTRAN Holdings, Inc.	(31,239)	$ (49,515)	$ (324,201)	(78,210)	$ (38,749)	$ (39,738)	$ (373,716)	$ (78,487)	(404,955)	(156,697)	$ (266,289)
Reclassification Out of Accumulated Other Comprehensive Income [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit plan adjustments - actuarial gain (loss)	(158)			120					(61)	36
Loss Before Income Taxes	(171)			441					(242)	403
Tax (expense) benefit	52			(114)					66	(99)
Net Loss attributable to ADTRAN Holdings, Inc.	(119)			327					(176)	304
Reclassification Out of Accumulated Other Comprehensive Income [Member] | Unrealized Gains (Losses) on Available-for-Sale Securities [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net realized gain (loss) on sales of securities	$ (13)			$ 321					$ (181)	$ 367

Equity - Tax Effects Related to

Equity - Tax Effects Related to the Change in Each Component of Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	3 Months Ended						6 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Equity [Abstract]
Unrealized (loss) gain on available-for-sale securities, Before-Tax Amount	$ (13)			$ 836					$ (181)	$ 964
Unrealized (loss) gain on available-for-sale securities, Tax (Expense) Benefit	3			(201)					47	(231)
Unrealized (loss) gain on available-for-sale securities, Net-of-Tax Amount	(10)			635					(134)	733
Reclassification adjustment for amounts related to available-for-sale investments included in net gain (loss), Before-Tax Amount	13			(321)					181	(367)
Reclassification adjustment for amounts related to available-for-sale investments included in net gain (loss), Tax (Expense) Benefit	(3)			77					(47)	88
Reclassification adjustment for amounts related to available-for-sale investments included in net gain (loss), Net-of-Tax Amount	10			(244)					134	(279)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net (loss) gain, Before-Tax Amount	158			(120)					61	(36)
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net (loss) gain, Tax (Expense) Benefit	(49)			37					(19)	11
Reclassification adjustment for amounts related to defined benefit plan adjustments included in net (loss) gain, Net-of-Tax Amount	109			(83)					42	(25)
Foreign currency translation adjustment, Before-Tax Amount	18,988			(29,715)					(130)	(14,095)
Foreign currency translation adjustment, Net-of-Tax Amount	18,988	$ (1,374)	$ (17,744)	(29,715)	$ 6,941	$ 8,679	$ (19,118)	$ 15,620	(130)	(14,095)	$ 22,757
Total Other Comprehensive (Loss) Income, Before-Tax Amount	19,146			(29,320)					(69)	(13,534)
Total Other Comprehensive (Loss) Income, Tax (Expense) Benefit	(49)			(87)					(19)	(132)
Other Comprehensive Income (Loss), net of tax	$ 19,097	$ (1,381)	$ (17,804)	$ (29,407)	$ 6,958	$ 8,783	$ (19,185)	$ 15,741	$ (88)	$ (13,666)	$ 21,721

Redeemable Non-controlling In_3

Redeemable Non-controlling Interest - Summary of Redeemable Non-controlling Interest Activity (Detail) - USD ($) $ in Thousands	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Dec. 31, 2023
Redeemable Noncontrolling Interest [Line Items]
Balance at beginning of period	$ 442,152
Reclassification of non-controlling interests		$ 443,757
Fair value on redemption of redeemable non-controlling interest	(20,376)	(1,657)
Net income attributable to redeemable non-controlling interests	7,417	10,092
Annual recurring compensation earned	(7,417)	(10,092)
Balance at end of period	$ 421,776	442,152
Adtran Networks [Member]
Redeemable Noncontrolling Interest [Line Items]
Stock option exercises		$ 52

Redeemable Non-controlling In_4

Redeemable Non-controlling Interest - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Dec. 31, 2023
Redeemable Noncontrolling Interest [Line Items]
Accrued annual recurring compensation to redeemable non-controlling shareholders	$ 2.4	$ 2.6	$ 7.4	$ 7.6
Annual recurring compensation paid to redeemable non-controlling shareholders					$ 10.1
Adtran Networks [Member]
Redeemable Noncontrolling Interest [Line Items]
Equity ownership percentage	33%		33%		34.60%

Loss Per Share - Summary of Cal

Loss Per Share - Summary of Calculation of Basic and Diluted Loss Per Share (Detail) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended							6 Months Ended		9 Months Ended			12 Months Ended
	Sep. 30, 2024		Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023	Sep. 30, 2024		Sep. 30, 2023	Dec. 31, 2023
Numerator
Net Loss attributable to ADTRAN Holdings, Inc.	$ (31,239)		$ (49,515)	$ (324,201)	$ (78,210)	$ (38,749)	$ (39,738)	$ (373,716)	$ (78,487)	$ (404,955)		$ (156,697)	$ (266,289)
Gain on redemption of redeemable non-controlling interest	2,976									2,976
Net loss attributable to ADTRAN Holdings, Inc. for loss per share computation	$ (28,263)				$ (78,210)					$ (401,979)		$ (156,697)
Denominator
Weighted average number of shares – basic	78,952				78,389					78,873		78,378
Effect of dilutive securities
Weighted average number of shares – diluted	78,952				78,389					78,873		78,378
Loss per share attributable to ADTRAN Holdings, Inc. - basic	$ (0.36)	[1]	$ (0.63)	$ (4.12)	$ (1)	$ (0.5)	$ (0.51)	$ (4.74)	$ (1)	$ (5.1)	[1]	$ (2)	$ (3.39)
Loss per share attributable to ADTRAN Holdings, Inc. - diluted	$ (0.36)	[1]	$ (0.63)	$ (4.12)	$ (1)	$ (0.5)	$ (0.51)	$ (4.74)	$ (1)	$ (5.1)	[1]	$ (2)	$ (3.39)
[1] Loss per common share attributable to ADTRAN Holdings, Inc. - basic and diluted - reflects a $ 3.0 million effect of redemption of RNCI for the three and nine months ended September 30, 2024. See Note 15 for additional information.

Loss Per Share - Additional Inf

Loss Per Share - Additional Information (Detail) - shares shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Antidilutive Securities Excluded From Computation Of Earnings Per Share [Line Items]
Anti-dilutive effect excluded calculation of diluted earnings per share	4	2.6	4.2	1.4
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	0.9	0.5	1.1	0.4

Segment Information - Additiona

Segment Information - Additional Information (Detail) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024 USD ($)	Sep. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) Segment	Sep. 30, 2023 USD ($)
Segment Reporting Information [Line Items]
Number of reportable segments | Segment			2
Depreciation expense	$ 8,700	$ 7,400	$ 24,500	$ 22,600
Network Solutions [Member]
Segment Reporting Information [Line Items]
Depreciation expense	2,900	1,500	7,400	4,500
Services & Support [Member]
Segment Reporting Information [Line Items]
Depreciation expense	$ 100	$ 2	$ 200	$ 7

Segment Information - Revenue a

Segment Information - Revenue and Gross Profit of Reportable Segments (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting Information [Line Items]
Revenue	$ 227,704	$ 272,331	$ 679,868	$ 923,621
Gross Profit	85,251	74,237	239,081	254,598
Network Solutions [Member]
Segment Reporting Information [Line Items]
Revenue	181,488	228,564	541,955	793,984
Gross Profit	55,713	47,277	156,472	176,607
Services & Support [Member]
Segment Reporting Information [Line Items]
Revenue	46,216	43,767	137,913	129,637
Gross Profit	$ 29,538	$ 26,960	$ 82,609	$ 77,991

Segment Information - Revenue I

Segment Information - Revenue Information by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Revenue from External Customer [Line Items]
Revenue	$ 227,704	$ 272,331	$ 679,868	$ 923,621
United States [Member]
Revenue from External Customer [Line Items]
Revenue	102,527	111,494	293,420	375,254
United Kingdom [Member]
Revenue from External Customer [Line Items]
Revenue	49,366	60,347	145,666	212,171
Germany [Member]
Revenue from External Customer [Line Items]
Revenue	27,270	41,242	91,553	150,710
Other International [Member]
Revenue from External Customer [Line Items]
Revenue	$ 48,541	$ 59,248	$ 149,229	$ 185,486

Liability for Warranty Return_2

Liability for Warranty Returns - Additional Information (Detail) - USD ($) $ in Thousands	9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Dec. 31, 2023	Sep. 30, 2023	Jun. 30, 2023	Dec. 31, 2022
Product Warranties Disclosures [Abstract]
Period of assurance-based warranty for product defects	90 days to five years
Liability for warranty obligations	$ 5,649	$ 6,024	$ 6,445	$ 6,567	$ 6,831	$ 7,196

Liability for Warranty Return_3

Liability for Warranty Returns - Summary of Warranty Expense and Write-off Activity (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Product Warranties Disclosures [Abstract]
Balance at beginning of period	$ 6,024	$ 6,831	$ 6,445	$ 7,196
Plus: Amounts charged to cost and expenses	395	752	1,779	2,289
Plus: Foreign currency translation adjustments	84	(73)	21	(33)
Less: Deductions	(854)	(943)	(2,596)	(2,885)
Balance at end of period	$ 5,649	$ 6,567	$ 5,649	$ 6,567

Commitments and Contingencies -

Commitments and Contingencies - Additional Information (Detail) shares in Thousands, $ in Thousands	3 Months Ended									6 Months Ended		9 Months Ended						12 Months Ended
	Sep. 30, 2024 USD ($) shares		Jun. 30, 2024 USD ($)	Mar. 31, 2024 USD ($)	Sep. 30, 2023 USD ($) shares		Sep. 30, 2023 EUR (€) shares	Jun. 30, 2023 USD ($)	Mar. 31, 2023 USD ($)	Jun. 30, 2024 USD ($)	Jun. 30, 2023 USD ($)	Sep. 30, 2024 USD ($) shares		Sep. 30, 2024 EUR (€) shares	Sep. 30, 2023 USD ($) shares		Sep. 30, 2023 EUR (€) shares	Dec. 31, 2023 USD ($)	Sep. 30, 2024 EUR (€)
Commitments And Contingencies Line Items
Aggregate exit compensation payments obligation including guaranteed interest	$ 364,100											$ 364,100							€ 326,900,000
Number of shares tendered | shares	830											831		831	64		64
Exit compensation payments					$ 9		€ 8,000					$ 17,400		€ 15,700,000	$ 1,200		€ 1,100
Percentage of guaranteed interest rate	5%											5%							5%
Percentage of guaranteed interest rate plus a variable component	3.37%											3.37%							3.37%
Annual recurring compensation obligation												$ 10,000		€ 8,900,000
Expire date of exit compensation												Mar. 16, 2023		Mar. 16, 2023
Accrued annual recurring compensation obligation	$ 2,400				2,600							$ 7,400			7,600
Annual recurring compensation paid																		$ 10,100
Commitments related to performance bonds	14,600											$ 14,600						10,800
Commitments related to performance bonds expiration month and year												2031-04		2031-04
Purchase obligations	261,800											$ 261,800
Less: Net Income attributable to non-controlling interest	$ 2,382	[1]	$ 2,504	$ 2,531	$ 2,561	[1]		$ 2,534	$ (715)	$ 5,035	$ 1,819	$ 7,417	[1]		$ 4,380	[1]		$ 6,946
Maximum [Member]
Commitments And Contingencies Line Items
Number of shares tendered | shares					1		1
[1] For the three and nine months ended September 30, 2024, we accrued $ 2.4 million and $ 7.4 million, respectively, net income attributable to non-controlling interest, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA. For the three and nine months ended September 30, 2023, we accrued $ 2.6 million and $ 7.6 million, respectively, representing the recurring cash compensation earned by non-controlling interest shareholders post-DPLTA, partially offset by a $ 3.2 million net loss attributable to non-controlling interests pre-DPLTA for the nine months ended September 30, 2023.

Restructuring - Additional Info

Restructuring - Additional Information (Detail) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended
	Nov. 06, 2023	Nov. 12, 2024	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023	Oct. 25, 2023
Restructuring Cost and Reserve [Line Items]
Reduction of workforce and hiring freeze							5%
Inventory write down					$ 4,135	$ 21,043
Restructuring Costs	$ 65,600		$ 5,900		40,600
Severance costs					6,200
Subsequent Events [Member]
Restructuring Cost and Reserve [Line Items]
Severance costs		$ 23,100
Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Expected costs in fourth quarter 2024			13,800		13,800
Site consolidation transaction expenses		7,600			7,600
Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Expected costs in fourth quarter 2024			9,600		9,600
Site consolidation transaction expenses		$ 3,400			$ 3,400
Multi-Year Integration Program and Synergy Realization [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs related to Business Combination				$ 24,900		33,200
Restructuring Charges, Statement of Income or Comprehensive Income [Extensible Enumeration]					Cost of Goods and Services Sold, Research and Development Expense, Selling, General and Administrative Expense
Business Efficiency Program
Restructuring Cost and Reserve [Line Items]
Strategy shift charges			$ (300)		$ 8,600
Inventory write down				$ 21,000	4,100
Other charges					$ 4,500
Network Solutions [Member]
Restructuring Cost and Reserve [Line Items]
Inventory write down						$ 21,000

Restructuring - Schedule of Rec

Restructuring - Schedule of Reconciliation of Restructuring Liability (Detail) - USD ($) $ in Thousands	3 Months Ended	9 Months Ended	12 Months Ended
	Sep. 30, 2024	Sep. 30, 2024	Dec. 31, 2023
Restructuring and Related Activities [Abstract]
Balance at beginning of period	$ 18,657	$ 8,309	$ 159
Plus: Amounts charged to cost and expense	5,936	36,441	22,241
Less: Amounts paid	(7,770)	(27,927)	(14,091)
Balance at end of period	$ 16,823	$ 16,823	$ 8,309

Restructuring - Schedule of Com

Restructuring - Schedule of Components of Restructuring Expenses Including in Condensed Consolidated Statements of (Loss) Income (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 5,936,000	$ 24,873,000	$ 40,576,000	$ 33,178,000
Cost of Sales [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	7,000	21,630,000	14,042,000	21,706,000
Cost of Sales [Member] | Network Solutions [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	517,000	611,000	3,359,000	669,000
Cost of Sales [Member] | Services & Support [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	(182,000)	(24,000)	2,086,000	(6,000)
Other (Credits), Charges and Inventory Write-Down [Member] | Network Solutions [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	(328,000)	21,043,000	8,597,000	21,043,000
Selling, General and Administrative Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	2,681,000	3,387,000	7,980,000	6,960,000
Research and Development Expenses [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 3,248,000	$ (144,000)	$ 18,554,000	$ 4,512,000

Restructuring - Schedule of C_2

Restructuring - Schedule of Components of Restructuring Expense by Geographic Area (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 5,936	$ 24,873	$ 40,576	$ 33,178
United States [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	1,208	22,598	17,495	25,217
International [Member]
Restructuring Cost And Reserve [Line Items]
Total restructuring expenses	$ 4,728	$ 2,275	$ 23,081	$ 7,961

Subsequent Events - Additional

Subsequent Events - Additional Information (Details) $ in Millions	12 Months Ended
	Dec. 31, 2023 USD ($)
Subsequent Event [Line Items]
Annual recurring compensation paid	$ 10.1