Schedule II - Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2015	Apr. 30, 2014	Apr. 30, 2013
Allowance for Doubtful Accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	$ 102	$ 148	$ 93
Additions (Reductions) Charged to Cost and Expenses	184	31	92
Other	0	0	0
Deductions	(113)	(77)	(37)
Balance at End of Year	173	102	148
Reserve for Cash Discounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	727	669	645
Additions (Reductions) Charged to Cost and Expenses	8,859	8,529	8,174
Other	0	0	0
Deductions	(8,840)	(8,471)	(8,150)
Balance at End of Year	746	727	669
Reserve for Sales Returns and Allowances [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Year	1,639	1,536	1,301
Additions (Reductions) Charged to Cost and Expenses	7,326	7,245	7,496
Other	0	0	0
Deductions	(7,371)	(7,142)	(7,261)
Balance at End of Year	$ 1,594	$ 1,639	$ 1,536