Inventories - Additional Information (Detail) (USD $)	12 Months Ended
	Apr. 30, 2014	Apr. 30, 2013
Inventories [Line Items]
LIFO inventory reserve	$ 1,200,000	$ 1,300,000
Increase or decrease in cost of sales as a result of liquidation of LIFO inventory	137,000	273,000
International Subsidiaries [Member]
Inventories [Line Items]
Inventories measured using FIFO method	$ 1,684,000	$ 2,077,000
Maximum [Member]
Inventories [Line Items]
LIFO index	100.00%