Inventories (Components Of Inventories) (Details) (USD $) In Thousands, unless otherwise specified	Jul. 31, 2014	Apr. 30, 2014
Inventory, Net [Abstract]
Raw materials	$ 16,039	$ 13,756
Work-in-process	19,746	19,179
Finished goods	14,532	13,439
Total FIFO inventories	50,317	46,374
Reserve to adjust inventories to LIFO value	(14,860)	(14,851)
Total LIFO inventories	$ 35,457	$ 31,523