Income Taxes: (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Oct. 27, 2012	Oct. 29, 2011	Oct. 27, 2012	Oct. 29, 2011
Income Taxes:
Effective tax rate (as a percent)	39.30%	31.20%	38.00%	33.70%
Reduction in income tax contingency reserves upon the expiration of the corresponding statute of limitations	$ 2.1	$ 0.2	$ 2.1	$ 0.6