Common stock transactions (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands			3 Months Ended			6 Months Ended
	Aug. 25, 2021	Mar. 17, 2021	Jul. 30, 2021	Apr. 30, 2021	Jul. 31, 2020	Jul. 30, 2021	Jul. 31, 2020
Common stock transactions
Aggregate purchase price			$ 699,796		$ 601,536	$ 1,700,148	$ 664,616
Cash dividend paid (in dollars per share)			$ 0.42	$ 0.42	$ 0.36	$ 0.84	$ 0.72
Subsequent event
Common stock transactions
Cash dividend declared (in dollars per share)	$ 0.42
Common Stock
Common stock transactions
Shares acquired under share repurchase program			3,309		3,184	8,268	3,635
Aggregate purchase price			$ 2,896		$ 2,785	$ 7,235	$ 3,180
Common Stock | Pursuant to Authorized Repurchase Program
Common stock transactions
Common stock repurchase program, increase in the authorized amount		$ 2,000,000
Common stock repurchase authorization		$ 12,000,000
Shares acquired under share repurchase program						8,300	3,600
Aggregate purchase price						$ 1,700,000	$ 700