Debt (Schedule of credit facilities) (Details) $ in Billions	12 Months Ended
	May 31, 2020 USD ($)
Line of Credit Facility [Line Items]
Facility Amount	$ 3.5
Borrowed Amount	0.2
Committed Credit Facilities [Member]
Line of Credit Facility [Line Items]
Facility Amount	2.9
Borrowed Amount	$ 0.0
Minimum fixed charge coverage ratio	2.5
Compliance with credit facility covenants	As of fiscal year end, we were in compliance with all credit facility covenants.
Line of Credit Expiring May 2022 [Member]
Line of Credit Facility [Line Items]
Facility Amount	$ 2.7
Borrowed Amount	$ 0.0
Expiration date of credit facility	May 31, 2022
Line Of Credit Expiring September 2022 [Member]
Line of Credit Facility [Line Items]
Facility Amount	$ 0.2
Borrowed Amount	0.0
Uncommitted Credit Facility [Member]
Line of Credit Facility [Line Items]
Facility Amount	0.6
Borrowed Amount	$ 0.2