Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2017	Jul. 31, 2016	Jul. 31, 2017	Jul. 31, 2016
Statement of Comprehensive Income [Abstract]
Net loss	$ (61,701)	$ (59,550)	$ (124,075)	$ (123,338)
Other comprehensive income:
Change in unrealized net gain on available-for-sale securities	165	45	282	852
Comprehensive loss	$ (61,536)	$ (59,505)	$ (123,793)	$ (122,486)