Net Income Per Share - Reconciliation of Denominator Used in Calculation of Basic and Diluted Earnings Per Share (Details) - USD ($) shares in Millions, $ in Millions	3 Months Ended						9 Months Ended
	Oct. 31, 2021	Jul. 31, 2021	Apr. 30, 2021	Oct. 31, 2020	Jul. 31, 2020	Apr. 30, 2020	Oct. 31, 2021	Oct. 31, 2020
Numerator:
Net income	$ 468	$ 535	$ 469	$ 1,081	$ 2,625	$ 99	$ 1,472	$ 3,805
Denominator:
Weighted-average shares outstanding for basic earnings per share (in shares)	980			911			945	905
Dilutive effect of employee stock awards (in shares)	21			28			19	21
Adjusted weighted-average shares outstanding and assumed conversions for diluted earnings per share (in shares)	1,001			939			964	926