Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2019	Apr. 30, 2018	Apr. 30, 2017
SEC Schedule, 12-09, Allowance, Credit Loss [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 259	$ 148	$ 171
Additions (Reductions) Charged to Cost and Expenses	72	169	200
Other	0	0	0
Deductions	(82)	(136)	(223)
Balance at End of Year	249	259	148
Reserve for Cash Discounts [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	1,627	979	827
Additions (Reductions) Charged to Cost and Expenses	16,994	11,999	10,027
Other	0	1	0
Deductions	(17,170)	(11,935)	(9,875)
Balance at End of Year	1,451	1,627	979
Reserve for Sales Returns and Allowances [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	4,381	2,131	1,782
Additions (Reductions) Charged to Cost and Expenses	11,867	11,318	7,962
Other	0	2	0
Deductions	(11,703)	(10,897)	(7,613)
Balance at End of Year	$ 4,545	$ 4,381	$ 2,131