CONDENSED CONSOLIDATED STATEMENTS OF COMPREHENSIVE LOSS - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Statement of Comprehensive Income [Abstract]
Net loss	$ (16,852)	$ (9,796)	$ (31,646)	$ (38,944)
Other comprehensive income
Unrealized gain (loss) on investment securities, net of tax	(49)	69	(411)	136
Total comprehensive loss	$ (16,901)	$ (9,727)	$ (32,057)	$ (38,808)