Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2020	Apr. 30, 2019	Apr. 30, 2018
Allowances for Accounts Receivable
Allowance Rollforward
Balance at beginning of period	$ (6,432)	$ (9,633)	$ (9,851)
Provision / Additions charged to costs and expenses	(2,348)	(1,064)	(366)
Charged to other accounts	938	2,435	(596)
Deductions	2,701	1,830	1,180
Balance at end of period	(5,141)	(6,432)	(9,633)
Valuation Allowance on Deferred Tax Assets
Allowance Rollforward
Balance at beginning of period	(1,112)	(448)	(297)
Provision / Additions charged to costs and expenses	(9,071)	(664)	(151)
Balance at end of period	$ (10,183)	$ (1,112)	$ (448)