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
	Mar. 31, 2026		Mar. 31, 2025		Mar. 31, 2024
Numerator
Net Loss attributable to ADTRAN Holdings, Inc.	$ (1,321)		$ (11,267)
Effect of redemption of RNCI	301		(3)
Net loss attributable to ADTRAN Holdings, Inc. common stockholders	$ (1,020)		$ (11,270)
Denominator
Weighted average number of shares – basic	80,321		79,534
Effect of dilutive securities
Weighted average number of shares – diluted	80,321		79,534		80,321
Loss per share attributable to ADTRAN Holdings, Inc. - basic	$ (0.01)	[1]	$ (0.14)	[1]	$ (0.01)
Loss per share attributable to ADTRAN Holdings, Inc. - diluted	$ (0.01)	[1]	$ (0.14)	[1]	$ (0.01)

[1] Loss per common share attributable to ADTRAN Holdings, Inc. - basic and diluted - reflects a $0.3 million and a $(3) thousand effect of redemption of RNCI for the three months ended March 31, 2026 and 2025. See Note 15 for additional information.