Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	12 Months Ended
	Jan. 31, 2018	Jan. 31, 2017	Jan. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (157,659)	$ (105,801)	$ (100,968)
Other comprehensive income (loss), net of taxes:
Unrealized gains on available-for-sale investments		14	(27)
Foreign currency translation adjustments	111	(274)	(28)
Comprehensive loss, net of taxes	$ (157,548)	$ (106,061)	$ (101,023)