Condensed Consolidated Statements of Comprehensive Loss - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Oct. 31, 2019	Oct. 31, 2018	Oct. 31, 2019	Oct. 31, 2018
Statement of Comprehensive Income [Abstract]
Net loss	$ (29,982)	$ (28,180)	$ (196,336)	$ (152,607)
Other comprehensive income (loss) net of tax:
Change in unrealized net gain (loss) on available-for-sale securities	1,707	(273)	5,454	(1,182)
Comprehensive loss	$ (28,275)	$ (28,453)	$ (190,882)	$ (153,789)