Summary of Significant Accounting Policies - Inventory (Details) - USD ($) $ in Thousands	12 Months Ended
Apr. 27, 2019	Apr. 28, 2018	Apr. 29, 2017
Accounting Policies [Abstract]
Inventories valued at LIFO as % of total inventories	82.00%	84.00%
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
LIFO inventory reserve	$ (91,342)	$ (82,105)
Increase to pre-tax income	106,228	179,263	$ 250,881
Change in LIFO Calculation Method
New Accounting Pronouncements or Change in Accounting Principle [Line Items]
LIFO inventory reserve		$ 1,800
Increase to pre-tax income	$ 1,800

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Amount of income (loss) from continuing operations, including income (loss) from equity method investments, before deduction of income tax expense (benefit), and income (loss) attributable to noncontrolling interest.

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Amount by which inventory stated at last-in first-out (LIFO) is less than (in excess of) inventory stated at other inventory cost methods.

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The percentage of LIFO (last in first out) inventory to total inventory as of the balance sheet date if other than 100 percent.

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