Fair Value Measurements (Details) (USD $) In Thousands, unless otherwise specified	Apr. 30, 2013	Jan. 31, 2013
Summary of assets and liabilities measured at fair value on a recurring basis
Money market funds (1)	$ 76,295	$ 68,971
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)	$ 76,295	$ 68,971