Stockholders' Equity - Narrative (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Billions	3 Months Ended		9 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019	Jan. 31, 2020
Equity [Abstract]
Weighted-average fair value per share of grants (in dollars per share)	$ 59.54	$ 35.31	$ 40.52	$ 39.65
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Share-based compensation expense			$ 1.6
Period for recognition			3 years
Total shares available for future grant (in shares)	143		143		133
Employee Stock
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Weighted-average fair value per share of ESPP shares (in dollars per share)	$ 53.64