Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 30, 2015	Apr. 30, 2014
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 173	$ 102	$ 148
Additions (Reductions) Charged to Cost and Expenses	108	184	31
Other	0	0	0
Deductions	(110)	(113)	(77)
Balance at End of Year	171	173	102
Reserve for Cash Discounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	746	727	669
Additions (Reductions) Charged to Cost and Expenses	9,570	8,859	8,529
Other	0	0	0
Deductions	(9,489)	(8,840)	(8,471)
Balance at End of Year	827	746	727
Reserve for Sales Returns and Allowances [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	1,594	1,639	1,536
Additions (Reductions) Charged to Cost and Expenses	7,833	7,326	7,245
Other	0	0	0
Deductions	(7,645)	(7,371)	(7,142)
Balance at End of Year	$ 1,782	$ 1,594	$ 1,639