Condensed Consolidated Statements of Comprehensive Loss (Unaudited) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jul. 31, 2019	Jul. 31, 2018	Jul. 31, 2019	Jul. 31, 2018
Statement Of Income And Comprehensive Income [Abstract]
Net loss	$ (10,191)	$ (6,877)	$ (27,502)	$ (16,883)
Other comprehensive income, net of tax:
Unrealized gains on investments	194	178	448	68
Other comprehensive income, net of tax	194	178	448	68
Comprehensive loss	$ (9,997)	$ (6,699)	$ (27,054)	$ (16,815)