Financial Instruments, Risk Management Activities, and Fair Values (Schedule of offsetting assets and liabilities) (Details) (USD $) In Millions, unless otherwise specified	Feb. 22, 2015	May 25, 2014
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	$ 44.3	$ 30.3
Gross Liabilities Offset in the Balance Sheet	0	0
Net Amounts of Assets	44.3	30.3
Financial Instruments, Gross Amounts Not Offset in the Balance Sheet	(24.4)	(11.4)
Cash Collateral Received, Gross Amounts Not Offset in the Balance Sheet	0	0
Net Amount	19.9	18.9
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	(143.1)	(23.1)
Gross Assets Offset in the Balance Sheet	0	0
Net Amounts of Liabilities	(143.1)	(23.1)
Financial Instruments, Gross Amounts Not Offset in the Balance Sheet	24.4	11.4
Cash Collateral Pledged, Gross Amounts Not Offset in the Balance Sheet	48.6	0
Net Amount	(70.1)	(11.7)
Commodity Contracts [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	4.6	19.1
Gross Liabilities Offset in the Balance Sheet	0	0
Net Amounts of Assets	4.6	19.1
Financial Instruments, Gross Amounts Not Offset in the Balance Sheet	(3.0)	(3.4)
Cash Collateral Received, Gross Amounts Not Offset in the Balance Sheet	0	0
Net Amount	1.6	15.7
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	(70.0)	(4.0)
Gross Assets Offset in the Balance Sheet	0	0
Net Amounts of Liabilities	(70.0)	(4.0)
Financial Instruments, Gross Amounts Not Offset in the Balance Sheet	3.0	3.4
Cash Collateral Pledged, Gross Amounts Not Offset in the Balance Sheet	48.6	0
Net Amount	(18.4)	(0.6)
Interest Rate Contracts [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	0.2	0.7
Gross Liabilities Offset in the Balance Sheet	0	0
Net Amounts of Assets	0.2	0.7
Financial Instruments, Gross Amounts Not Offset in the Balance Sheet	0	0
Cash Collateral Received, Gross Amounts Not Offset in the Balance Sheet	0	0
Net Amount	0.2	0.7
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	(2.5)	0
Gross Assets Offset in the Balance Sheet	0	0
Net Amounts of Liabilities	(2.5)	0
Financial Instruments, Gross Amounts Not Offset in the Balance Sheet	0	0
Cash Collateral Pledged, Gross Amounts Not Offset in the Balance Sheet	0	0
Net Amount	(2.5)	0
Foreign Exchange Contracts [Member]
Offsetting Assets [Line Items]
Gross Amounts of Recognized Assets	39.5	10.5
Gross Liabilities Offset in the Balance Sheet	0	0
Net Amounts of Assets	39.5	10.5
Financial Instruments, Gross Amounts Not Offset in the Balance Sheet	(21.4)	(8.0)
Cash Collateral Received, Gross Amounts Not Offset in the Balance Sheet	0	0
Net Amount	18.1	2.5
Offsetting Liabilities [Line Items]
Gross Amounts of Recognized Liabilities	(70.6)	(19.1)
Gross Assets Offset in the Balance Sheet	0	0
Net Amounts of Liabilities	(70.6)	(19.1)
Financial Instruments, Gross Amounts Not Offset in the Balance Sheet	21.4	8.0
Cash Collateral Pledged, Gross Amounts Not Offset in the Balance Sheet	0	0
Net Amount	$ (49.2)	$ (11.1)