Earnings Per Share ("EPS") - Computation of Basic and Diluted EPS (Detail) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Numerator:
Net income attributable to DNOW Inc.	$ 247	$ 128	$ 5
Less: net income attributable to participating securities	(4)	(2)	0
Net income attributable to DNOW Inc. stockholders	$ 243	$ 126	$ 5
Denominator:
Weighted average basic common shares outstanding	107,395,890	110,676,078	110,403,853
Effect of dilutive securities	1,026,865	548,311	91,088
Weighted average diluted common shares outstanding	108,422,755	111,224,389	110,494,941
Basic	$ 2.26	$ 1.14	$ 0.05
Diluted	$ 2.24	$ 1.13	$ 0.05