Fair Value Measurement (Details 1) - USD ($) $ in Thousands	Oct. 31, 2015	Jan. 31, 2015
Amortized Cost
Mature in one year or less	$ 34,142	$ 15,850
Mature after one year through five years	30,582	22,447
Total	64,724	38,297
Fair Market Value
Mature in one year or less	34,154	15,859
Mature after one year through five years	30,597	22,471
Total Fair Market Value	64,751	$ 38,330
Changes among the fair value levels
Changes between Level 1 to Level 2, Assets	$ 0