v3.26.1
Equity - Reclassifications Out of Accumulated Other Comprehensive Income (Detail) - USD ($)
$ in Thousands
3 Months Ended 6 Months Ended
Jun. 30, 2026
Jun. 30, 2025
Jun. 30, 2026
Jun. 30, 2025
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]        
Loss Before Income Taxes $ (7,916) $ (17,242) $ (5,069) $ (26,587)
Tax (expense) benefit (788) (1,016) (2,705) (619)
Net Loss attributable to ADTRAN Holdings, Inc. (10,905) (20,531) (12,226) (31,798)
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 gain (loss) (71) 388 (167) 578
Loss Before Income Taxes (53) 426 (170) 551
Tax (expense) benefit 17 (130) 53 (172)
Net Loss attributable to ADTRAN Holdings, Inc. (36) 296 (117) 379
Reclassification Out of Accumulated Other Comprehensive Income (Loss) [Member] | Unrealized Gains (Losses) on Available-for-Sale Securities [Member]        
Reclassification Adjustment Out of Accumulated Other Comprehensive Income (Loss) [Line Items]        
Net realized gain (loss) on sales of securities $ 18 $ 38 $ (3) $ (27)