Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 30, 2016	Apr. 25, 2015	Apr. 26, 2014
Allowance for doubtful accounts [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 7,678	$ 8,322	$ 4,093
Charged to Costs and Expenses	8,246	2,546	2,544
Charged to Other Accounts	1,947	0	3,552
Deductions	5,863	3,190	1,867
Balance at End of Period	12,008	7,678	8,322
LIFO inventory adjustment [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	73,381	71,596	67,187
Charged to Costs and Expenses	3,120	1,785	4,409
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Balance at End of Period	76,501	73,381	71,596
Inventory obsolescence reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	4,218	3,498	3,288
Charged to Costs and Expenses	15,547	17,624	12,642
Charged to Other Accounts	1,550	0	391
Deductions	14,694	16,904	12,823
Balance at End of Period	6,621	4,218	3,498
Total inventory reserve [Member]
Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	77,599	75,094	70,475
Charged to Costs and Expenses	18,667	19,409	17,051
Charged to Other Accounts	1,550	0	391
Deductions	14,694	16,904	12,823
Balance at End of Period	$ 83,122	$ 77,599	$ 75,094