Income taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		6 Months Ended
	Aug. 03, 2012	Jul. 29, 2011	Aug. 03, 2012	Jul. 29, 2011
Income taxes
Threshold level used to determine the amount of eligible uncertain tax benefits to be recorded (as a percentage)			50.00%
Reserves for uncertain tax benefits	$ 21.3		$ 21.3
Interest accrued related to uncertain tax benefits	1.8		1.8
Penalties accrued related to uncertain tax benefits	0.4		0.4
Aggregate reserve for uncertain tax positions including interest and penalties	23.5		23.5
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	22.9		22.9
Reduction of deferred tax assets related to net operating loss carry forwards	0.3		0.3
Decrease in reserve for uncertain tax benefits due to favorable resolution of matters associated with examination activity	20.7		20.7
Reasonably possible reduction in reserve for uncertain tax positions in next twelve months	1.0		1.0
Reserve for uncertain tax positions that would impact effective tax rate if recognized	$ 21.3		$ 21.3
Effective income tax rates (as a percent)	34.10%	36.80%	36.20%	37.50%