Revenue Recognition - Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Jan. 31, 2021	Jan. 31, 2020	Jan. 31, 2021	Jan. 31, 2020
Revenues:
Revenues	$ 27,683	$ 30,600	$ 82,842	$ 86,193
Domestic
Revenues:
Revenues	23,668	24,902	70,467	69,076
International
Revenues:
Revenues	$ 4,015	$ 5,698	$ 12,375	$ 17,117