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				6 Months Ended
	Jul. 31, 2020	Apr. 30, 2020	Jul. 31, 2019	Apr. 30, 2019	Jul. 31, 2020	Jul. 31, 2019
Numerator:
Net income	$ 2,625	$ 99	$ 91	$ 392	$ 2,724	$ 483
Denominator:
Weighted-average shares outstanding for basic earnings per share (in shares)	904		776		901	774
Dilutive effect of employee stock awards (in shares)	18		19		18	21
Adjusted weighted-average shares outstanding and assumed conversions for diluted earnings per share (in shares)	922		795		919	795