Inventories (Components Of Inventories) (Details) (USD $) In Thousands, unless otherwise specified	Oct. 31, 2013	Apr. 30, 2013
Inventories [Abstract]
Raw materials	$ 12,980	$ 11,823
Work-in-process	17,007	17,170
Finished goods	12,130	11,318
Total FIFO inventories	42,117	40,311
Reserve to adjust inventories to LIFO value	(10,986)	(10,973)
Total LIFO inventories	$ 31,131	$ 29,338