Fair Value Measurements - Fair Value of Assets Measured at Fair Value on Recurring Basis (Details) - Fair Value Measurements Recurring - USD ($) $ in Thousands	Jul. 31, 2016	Jan. 31, 2016
Restricted cash:
Total assets measured at fair value	$ 27,128	$ 35,331
Corporate Debt Securities
Marketable securities:
Marketable securities		5,559
Certificates Of Deposit
Restricted cash:
Restricted cash	26,968	26,968
Asset-backed Securities
Marketable securities:
Marketable securities		1,820
Money Market Funds
Restricted cash:
Restricted cash	160	984
Level 1
Restricted cash:
Total assets measured at fair value	160	984
Level 1 | Money Market Funds
Restricted cash:
Restricted cash	160	984
Level 2
Restricted cash:
Total assets measured at fair value	26,968	34,347
Level 2 | Corporate Debt Securities
Marketable securities:
Marketable securities		5,559
Level 2 | Certificates Of Deposit
Restricted cash:
Restricted cash	$ 26,968	26,968
Level 2 | Asset-backed Securities
Marketable securities:
Marketable securities		$ 1,820