Income taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Nov. 02, 2012	Oct. 28, 2011	Nov. 02, 2012	Oct. 28, 2011
Income taxes
Reserves for uncertain tax benefits	$ 22.7		$ 22.7
Interest accrued related to uncertain tax benefits	2.1		2.1
Penalties accrued related to uncertain tax benefits	0.4		0.4
Aggregate reserve for uncertain tax positions including interest and penalties	25.2		25.2
Reserves for uncertain tax benefits included in current liabilities as accrued expenses and other	0.3		0.3
Reserves for uncertain tax benefits included in noncurrent other liabilities	24.9		24.9
Decrease in reserve for uncertain tax benefits due to favorable resolution of matters associated with examination activity	19.3		19.3
Reserve for uncertain tax positions that would impact effective tax rate if recognized	22.7		22.7
Reserve for uncertain tax positions for which a reduction is reasonably possible in next twelve months	$ 15.0		$ 15.0
Effective income tax rates (as a percent)	37.40%	37.10%	36.60%	37.40%