Income taxes (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	May 04, 2012	Apr. 29, 2011
Income taxes
Threshold level (as a percentage) used to determine the amount of eligible uncertain tax benefits to be recorded	50.00%
Reserves for uncertain tax benefits	$ 37.9
Interest accrued related to uncertain tax benefits	1.5
Penalties accrued related to uncertain tax benefits	0.3
Aggregate reserve for uncertain tax positions including interest and penalties	39.7
Reserves for uncertain tax benefits included in current liabilities as accrued expenses and other	0.3
Reserves for uncertain tax benefits included in noncurrent other liabilities	38.1
Reduction of deferred tax assets related to net operating loss carry forwards	1.3
Reasonably possible reduction in reserve for uncertain tax position in next twelve months	26.2
Reserve for uncertain tax positions that would impact effective tax rate if recognized	$ 37.9
Effective income tax rate (as a percent)	38.20%	38.10%