Income Taxes (Effective Income Tax Rate Reconciliation) (Details)	12 Months Ended
May 31, 2020	May 26, 2019	May 27, 2018
Income Tax Disclosure [Abstract]
U.S. statutory rate	21.00%	21.00%	29.40%
State and local income taxes, net of federal tax benefits	3.70%	2.40%	1.80%
Enactment of the Tax Cuts and Jobs Act	0	0	(0.131)
Benefit of federal income tax credits	47.30%	(10.80%)	(12.80%)
Stock-based compensation tax benefit	5.00%	(2.00%)	(1.80%)
Nondeductible goodwill impairment	(16.40%)	0.00%	0.00%
Deferred revaluation	6.30%	0.00%	0.00%
Other, net	2.50%	(2.50%)	(3.20%)
Effective income tax rate	69.40%	8.10%	0.30%

Percentage of current income tax expense (benefit) and deferred income tax expense (benefit) pertaining to continuing operations.

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Percentage of domestic federal statutory tax rate applicable to pretax income (loss).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to changes in the valuation allowance for deferred tax assets.

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Percentage of difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operation, attributable to expense for award under share-based payment arrangement. Excludes expense determined to be nondeductible upon grant or after for award under share-based payment arrangement.

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations applicable to state and local income tax expense (benefit), net of federal tax expense (benefit).

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Percentage of the difference between reported income tax expense (benefit) and expected income tax expense (benefit) computed by applying the domestic federal statutory income tax rates to pretax income (loss) from continuing operations attributable to tax credits. Including, but not limited to, research credit, foreign tax credit, investment tax credit, and other tax credits.

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Percentage of reported income tax expense (benefit) in excess of (less than) expected income tax expense (benefit) computed by applying domestic federal statutory income tax rate to pretax income (loss) from continuing operations, attributable to Tax Cuts and Jobs Act.

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