Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 27, 2019	Apr. 28, 2018	Apr. 29, 2017
Allowance for doubtful accounts [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 9,537	$ 9,342	$ 12,008
Charged to Costs and Expenses	7,333	6,280	1,825
Charged to Other Accounts	0	0	0
Deductions	10,098	6,085	4,491
Balance at End of Period	6,772	9,537	9,342
LIFO inventory adjustment [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	82,105	77,816	76,501
Charged to Costs and Expenses	9,237	4,289	1,315
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Balance at End of Period	91,342	82,105	77,816
Inventory obsolescence reserve [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	5,376	5,621	6,621
Charged to Costs and Expenses	30,995	22,919	18,026
Charged to Other Accounts	0	0	0
Deductions	26,272	23,164	19,026
Balance at End of Period	10,099	5,376	5,621
Total inventory reserve [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	87,481	83,437	83,122
Charged to Costs and Expenses	40,232	27,208	19,341
Charged to Other Accounts	0	0	0
Deductions	26,272	23,164	19,026
Balance at End of Period	$ 101,441	$ 87,481	$ 83,437