Inventories (Details) (USD $)	3 Months Ended
	Oct. 25, 2014	Apr. 26, 2014
Inventories
Raw materials	$ 74,707,000	$ 71,247,000
Work in process	11,912,000	13,722,000
Finished goods	99,312,000	91,842,000
FIFO inventories	185,931,000	176,811,000
Excess of FIFO over LIFO	(27,605,000)	(29,802,000)
Inventories, net	158,326,000	147,009,000
Adjustment to LIFO reserve	$ 2,000,000