Financial Instruments, Risk Management Activities, and Fair Values (Schedule of fair value measurement inputs) (Details) (USD $) In Millions, unless otherwise specified	Aug. 26, 2012	May 27, 2012
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other Assets Fair Value Disclosure	$ 22.6	$ 57.6
Total Assets Fair Value Disclosure	73.1	99.2
Other Liabilities Fair Value Disclosure	0	0
Total Liabilities Fair Value Disclosure	(32.3)	(55.7)
Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	8.1	17.2
Derivative Liability Fair Value	(17.5)	(18.8)
Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	42.4	24.4
Derivative Liability Fair Value	(14.8)	(36.9)
Fair Value Inputs Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other Assets Fair Value Disclosure	5.6	5.3
Total Assets Fair Value Disclosure	5.8	13.3
Other Liabilities Fair Value Disclosure	0	0
Total Liabilities Fair Value Disclosure	0	0
Fair Value Inputs Level 1 [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Fair Value Inputs Level 1 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0.2	8.0
Derivative Liability Fair Value	0	0
Fair Value Inputs Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other Assets Fair Value Disclosure	17.0	52.3
Total Assets Fair Value Disclosure	67.3	85.9
Other Liabilities Fair Value Disclosure		0
Total Liabilities Fair Value Disclosure	(32.3)	(55.7)
Fair Value Inputs Level 2 [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	8.1	17.2
Derivative Liability Fair Value	(17.5)	(18.8)
Fair Value Inputs Level 2 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	42.2	16.4
Derivative Liability Fair Value	(14.8)	(36.9)
Fair Value Inputs Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other Assets Fair Value Disclosure	0	0
Total Assets Fair Value Disclosure	0	0
Other Liabilities Fair Value Disclosure	0	0
Total Liabilities Fair Value Disclosure	0	0
Fair Value Inputs Level 3 [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Fair Value Inputs Level 3 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Interest Rate Contract Fair Value [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	4.3	5.7
Derivative Liability Fair Value	0	0
Interest Rate Contract Fair Value [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0.2	0.5
Derivative Liability Fair Value	0	0
Interest Rate Contract Fair Value [Member] | Fair Value Inputs Level 1 [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Interest Rate Contract Fair Value [Member] | Fair Value Inputs Level 1 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Interest Rate Contract Fair Value [Member] | Fair Value Inputs Level 2 [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	4.3	5.7
Derivative Liability Fair Value	0	0
Interest Rate Contract Fair Value [Member] | Fair Value Inputs Level 2 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0.2	0.5
Derivative Liability Fair Value	0	0
Interest Rate Contract Fair Value [Member] | Fair Value Inputs Level 3 [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Interest Rate Contract Fair Value [Member] | Fair Value Inputs Level 3 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Foreign Exchange Contract Fair Value [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	3.8	11.5
Derivative Liability Fair Value	(17.5)	(18.8)
Foreign Exchange Contract Fair Value [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	2.0	6.6
Derivative Liability Fair Value	(0.7)	(1.1)
Foreign Exchange Contract Fair Value [Member] | Fair Value Inputs Level 1 [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Foreign Exchange Contract Fair Value [Member] | Fair Value Inputs Level 1 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Foreign Exchange Contract Fair Value [Member] | Fair Value Inputs Level 2 [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	3.8	11.5
Derivative Liability Fair Value	(17.5)	(18.8)
Foreign Exchange Contract Fair Value [Member] | Fair Value Inputs Level 2 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	2.0	6.6
Derivative Liability Fair Value	(0.7)	(1.1)
Foreign Exchange Contract Fair Value [Member] | Fair Value Inputs Level 3 [Member] | Designated as Hedging Instrument [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Foreign Exchange Contract Fair Value [Member] | Fair Value Inputs Level 3 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Commodity Contract Fair Value [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	22.7	9.0
Derivative Liability Fair Value	(5.4)	(15.1)
Commodity Contract Fair Value [Member] | Fair Value Inputs Level 1 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0.2	8.0
Derivative Liability Fair Value	0	0
Commodity Contract Fair Value [Member] | Fair Value Inputs Level 2 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	22.5	1.0
Derivative Liability Fair Value	(5.4)	(15.1)
Commodity Contract Fair Value [Member] | Fair Value Inputs Level 3 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Grain Contracts [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	17.5	8.3
Derivative Liability Fair Value	(8.4)	(20.6)
Grain Contracts [Member] | Fair Value Inputs Level 1 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Grain Contracts [Member] | Fair Value Inputs Level 2 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	17.5	8.3
Derivative Liability Fair Value	(8.4)	(20.6)
Grain Contracts [Member] | Fair Value Inputs Level 3 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Marketable Investments [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other Assets Fair Value Disclosure	22.6	57.6
Other Liabilities Fair Value Disclosure	0	0
Marketable Investments [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	(0.3)	(0.1)
Marketable Investments [Member] | Fair Value Inputs Level 1 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other Assets Fair Value Disclosure	5.6	5.3
Other Liabilities Fair Value Disclosure	0	0
Marketable Investments [Member] | Fair Value Inputs Level 1 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	0	0
Marketable Investments [Member] | Fair Value Inputs Level 2 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other Assets Fair Value Disclosure	17.0	52.3
Other Liabilities Fair Value Disclosure		0
Marketable Investments [Member] | Fair Value Inputs Level 2 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	(0.3)	(0.1)
Marketable Investments [Member] | Fair Value Inputs Level 3 [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Other Assets Fair Value Disclosure	0	0
Other Liabilities Fair Value Disclosure	0	0
Marketable Investments [Member] | Fair Value Inputs Level 3 [Member] | Not Designated as Hedging [Member]
Fair Value Balance Sheet Grouping Financial Statement Captions [Line Items]
Derivative Asset Fair Value	0	0
Derivative Liability Fair Value	$ 0	$ 0