Financial Instruments, Risk Management Activities, and Fair Values (Schedule of available for sale securities) (Details) - USD ($) $ in Millions	12 Months Ended
May 31, 2020	May 26, 2019
FINANCIAL INSTRUMENTS, RISK MANAGEMENT ACTIVITIES, AND FAIR VALUES [Abstract]
Cost	$ 56.7	$ 34.3
Cost	0.3	0.6
Cost, Total	57.0	34.9
Fair Value	56.7	34.3
Fair Value	4.9	18.5
Fair Value, Total	61.6	52.8
Gross Gains	0.0	0.0
Gross Gains	4.6	17.9
Gross Gains, Total	4.6	17.9
Gross Losses	0.0	0.0
Gross Losses	0.0	0.0
Gross Losses, Total	$ 0.0	$ 0.0

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amortized cost of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount of unrealized gain (loss) on investment in debt and equity securities.

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Amount of unrealized gain (loss) recognized in earnings from investment in debt and equity securities measured at fair value with change in fair value recognized in net income, and recognized from transfer of investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale) and investment in debt security measured at amortized cost (held-to-maturity) to investment in debt security measured at fair value with change in fair value recognized in net income (trading). Excludes other-than-temporary impairment (OTTI).

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Cost of investment in debt investment in debt security measured at fair value with change in fair value recognized in net income (trading) and investment in equity security with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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Amount of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Cost of investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI). Excludes equity method investment and investment in equity security without readily determinable fair value.

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Amount of unrealized gain on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of unrealized loss on investment in equity security measured at fair value with change in fair value recognized in net income (FV-NI).

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Amount of investment in marketable security.

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