Segment reporting (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2015 USD ($) segment	Aug. 01, 2014 USD ($) segment	Jul. 31, 2015 USD ($) segment	Aug. 01, 2014 USD ($) segment
Segment reporting
Number of reportable segments | segment	1	1	1	1
Net sales data for classes of similar products
Net sales	$ 5,095,904	$ 4,724,039	$ 10,014,576	$ 9,246,120
Consumables
Net sales data for classes of similar products
Net sales	3,867,635	3,576,189	7,621,613	7,021,654
Seasonal
Net sales data for classes of similar products
Net sales	642,525	593,596	1,228,818	1,135,028
Home products
Net sales data for classes of similar products
Net sales	304,305	285,428	607,329	569,025
Apparel
Net sales data for classes of similar products
Net sales	$ 281,439	$ 268,826	$ 556,816	$ 520,413