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Summary of Significant Accounting Policies - Fair Value Information (Details) (Fair Value, Measurements, Recurring [Member], USD $)
In Thousands, unless otherwise specified |
Jan. 31, 2015
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Feb. 01, 2014
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|---|---|---|
| Fair Value, Inputs, Level 1 [Member] | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| U.S. treasury securities money market funds | $ 166,602 | $ 290,361 |
| Fair Value, Inputs, Level 2 [Member] | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| U.S. treasury securities money market funds | 0 | 0 |
| Fair Value, Inputs, Level 3 [Member] | ||
| Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items] | ||
| U.S. treasury securities money market funds | $ 0 | $ 0 |