Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Jan. 31, 2013	Jan. 31, 2012
Summary of assets and liabilities measured at fair value on a recurring basis
Money market funds (1)	$ 68,971	$ 78,669
Quoted Prices in Active Markets for Identical Assets (Level 1) [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Money market funds (1)	68,971	78,669
Significant Other Observable Inputs (Level 2) [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Money market funds (1)
Significant Unobservable Inputs (Level 3) [Member]
Summary of assets and liabilities measured at fair value on a recurring basis
Money market funds (1)