Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (66,018)	$ (60,123)	$ (166,354)	$ (124,427)
Other comprehensive income (loss) net of tax:
Change in unrealized net gain (loss) on available-for-sale securities	2,120	(193)	3,747	(909)
Comprehensive loss	$ (63,898)	$ (60,316)	$ (162,607)	$ (125,336)