Schedule II Valuation and Qualifying Accounts (Details) - USD ($) $ in Thousands	12 Months Ended
	Apr. 25, 2020	Apr. 27, 2019	Apr. 28, 2018
Allowance for doubtful accounts [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	$ 6,772	$ 9,537	$ 9,342
Charged to Costs and Expenses	2,008	7,333	6,280
Charged to Other Accounts	0	0	0
Deductions	3,657	10,098	6,085
Balance at End of Period	5,123	6,772	9,537
LIFO inventory adjustment [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	91,342	82,105	77,816
Charged to Costs and Expenses	8,384	9,237	4,289
Charged to Other Accounts	0	0	0
Deductions	0	0	0
Balance at End of Period	99,726	91,342	82,105
Inventory obsolescence reserve [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	10,099	5,376	5,621
Charged to Costs and Expenses	27,405	30,995	22,919
Charged to Other Accounts	0	0	0
Deductions	11,978	26,272	23,164
Balance at End of Period	25,526	10,099	5,376
Total inventory reserve [Member]
SEC Schedule, 12-09, Movement in Valuation Allowances and Reserves [Roll Forward]
Balance at Beginning of Period	101,441	87,481	83,437
Charged to Costs and Expenses	35,789	40,232	27,208
Charged to Other Accounts	0	0	0
Deductions	11,978	26,272	23,164
Balance at End of Period	$ 125,252	$ 101,441	$ 87,481