Stock Repurchase Program (Details) - Common Stock Repurchase Program - $ / shares shares in Millions	12 Months Ended
	Jan. 31, 2020	Jan. 31, 2019	Jan. 31, 2018
Class of Stock [Line Items]
Repurchase and retirement of common shares (in shares)	2.7	2.2	6.9
Average repurchase price per share (in dollars per share)	$ 168.63	$ 130.15	$ 100.45
Common stock shares remained available for repurchase under repurchase plans (in shares)	14.7