Earnings Per Share - Computation of Basic and Diluted Earnings Per Share (Detail) - USD ($) $ / shares in Units, $ in Millions	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Numerator:
Net income attributable to NOW Inc.	$ 31	$ 30
Less: net income attributable to participating securities	0	0
Net income attributable to NOW Inc. stockholders	$ 31	$ 30
Denominator:
Weighted average basic common shares outstanding	110,006,858	110,602,943
Effect of dilutive securities	1,209,998	219,574
Weighted average diluted common shares outstanding	111,216,856	110,822,517
Basic	$ 0.28	$ 0.27
Diluted	$ 0.28	$ 0.27