Revenue Recognition - Disaggregated Revenue (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Oct. 31, 2020	Oct. 31, 2019	Oct. 31, 2020	Oct. 31, 2019
Revenues:
Revenues	$ 27,881	$ 28,210	$ 55,159	$ 55,593
Domestic
Revenues:
Revenues	23,659	22,763	46,799	44,174
International
Revenues:
Revenues	$ 4,222	$ 5,447	$ 8,360	$ 11,419