Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2017	Oct. 31, 2016	Oct. 31, 2017	Oct. 31, 2016
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (37,925)	$ (23,770)	$ (120,272)	$ (80,253)
Other comprehensive income (loss), net of taxes:
Unrealized gains on available-for-sale investments		2		14
Foreign currency translation adjustments	12	(157)	141	(261)
Comprehensive loss, net of taxes	$ (37,913)	$ (23,925)	$ (120,131)	$ (80,500)