Common stock transactions (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Millions		3 Months Ended		6 Months Ended
	Aug. 26, 2015	Jul. 31, 2015	May. 01, 2015	Jul. 31, 2015	Aug. 01, 2014
Common stock transactions
Cash dividend paid (in dollars per share)		$ 0.22	$ 0.22	$ 0.44
Cash dividend declared (in dollars per share)	$ 0.22
Common Stock | Pursuant to Authorized Repurchase Program
Common stock transactions
Common stock repurchase authorization		$ 3,000.0		$ 3,000.0
Remaining authorization available under the common stock repurchase program		$ 489.1		$ 489.1
Shares acquired under share repurchase program				9.7	14.1
Aggregate purchase price				$ 734.3	$ 800.1