Current and long-term obligations (Details) (USD $)	3 Months Ended	0 Months Ended							3 Months Ended
	May 03, 2013	Apr. 11, 2013 Senior unsecured credit facilities, maturity April 11, 2018	Aug. 01, 2014 Senior unsecured credit facility, maturity April 11, 2018, Term Facility	Apr. 11, 2013 Senior unsecured credit facility, maturity April 11, 2018, Term Facility	May 02, 2014 Senior unsecured credit facility, maturity April 11, 2018, Revolving Facility	Apr. 11, 2013 Senior unsecured credit facility, maturity April 11, 2018, Revolving Facility	May 02, 2014 Senior unsecured credit facility, maturity April 11, 2018, Revolving Facility Letters of credit	Apr. 11, 2013 Senior unsecured credit facility, maturity April 11, 2018, Revolving Facility Letters of credit	May 03, 2013 Previous Senior Secured Credit Facilities	Apr. 11, 2013 1.875% Senior Notes due April 15, 2018	Apr. 11, 2013 3.25% Senior Notes due April 15, 2023	Apr. 11, 2013 2018 and 2023 Senior Notes	May 02, 2014 Other letters of credit
Current and long-term obligations
Credit agreement term		5 years
Amount borrowed				$ 1,000,000,000						$ 400,000,000	$ 900,000,000
Maximum financing under credit agreements						850,000,000		250,000,000
Amount of quarterly installments beginning August 1, 2014			25,000,000
Debt issue cost capitalized		5,900,000										10,100,000
Amount of outstanding borrowings					290,000,000
Letters of credit outstanding							26,000,000						23,000,000
Borrowing availability under credit facility					534,000,000
Loss on debt retirement, net	18,871,000								18,900,000
Discount on debt issuance										$ 500,000	$ 2,400,000
Stated interest rate (as a percent)										1.875%	3.25%