Fair Value (Details Textuals) (USD $) In Millions, unless otherwise specified	6 Months Ended
	Jul. 30, 2011
Level 1 [Member] | Money market funds [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Fair value of Money market funds recorded as Cash Equivalents	161.0
Fair Value, Measured on Recurring Basis, Investments	0.6
Standard & Poor's, AAA Rating [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Percent of ARS Rating	45.00%
Standard & Poor's, AA Rating [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Percent of ARS Rating	20.00%
Standard & Poor's, A- Rating [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis, Valuation Techniques [Line Items]
Percent of ARS Rating	35.00%