CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands		12 Months Ended
		Jan. 31, 2017	Jan. 31, 2016	Jan. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net loss		$ (151,787)	$ (202,948)	$ (168,227)
Other comprehensive loss:
Changes in foreign currency translation adjustment	[1]	(37)	(26)	(71)
Net change in unrealized gains on available-for-sale investments	[1]	2	(2)
Other comprehensive loss:	[1]	(36)	(28)	(71)
Comprehensive loss		$ (151,823)	$ (202,976)	$ (168,298)

[1] Tax effect was not material