Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
Allowances for Accounts Receivable
Allowance Rollforward
Balance at beginning of period	$ (9,633)	$ (9,851)	$ (8,607)
Provision / Additions charged to costs and expenses	(1,064)	(366)	(1,792)
Charged to other accounts	2,435	(596)	(819)
Deductions	1,830	1,180	1,367
Balance at end of period	(6,432)	(9,633)	(9,851)
Valuation Allowance on Deferred Tax Assets
Allowance Rollforward
Balance at beginning of period	(448)	(297)	(83)
Provision / Additions charged to costs and expenses	(664)	(151)	(255)
Deductions			41
Balance at end of period	$ (1,112)	$ (448)	$ (297)