Common stock transactions (Details) - USD ($) $ / shares in Units, shares in Millions, $ in Billions		3 Months Ended			9 Months Ended
	Dec. 02, 2015	Oct. 30, 2015	Jul. 31, 2015	May. 01, 2015	Oct. 30, 2015	Oct. 31, 2014
Common stock transactions
Cash dividend paid (in dollars per share)		$ 0.22	$ 0.22	$ 0.22	$ 0.66
Cash dividend declared (in dollars per share)	$ 0.22
Common Stock | Pursuant to Authorized Repurchase Program
Common stock transactions
Common stock repurchase program, increase in the authorized amount	$ 1.0
Common stock repurchase authorization	4.0
Remaining authorization available under the common stock repurchase program	$ 1.2
Shares acquired under share repurchase program					13.4	14.1
Aggregate purchase price					$ 1.0	$ 0.8