Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Loss) (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit plan adjustments – actuarial losses	$ 1,791	$ (11,128)
Loss Before Income Taxes	(231,210)	(70,963)	$ (6,305)
Tax (benefit) expense	(28,133)	62,075	(2,330)
Net Loss attributable to ADTRAN Holdings, Inc.	(267,688)	(2,037)	(8,635)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Defined benefit plan adjustments – actuarial losses	(145)	(113)	(825)
Loss Before Income Taxes	233	215	(989)
Tax (benefit) expense	(53)	(50)	299
Net Loss attributable to ADTRAN Holdings, Inc.	180	165	(690)
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] | Unrealized (Loss) Gain on Available-for-Sale Securities [Member]
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]
Net investment gain	$ 378	$ 328	$ (164)