Retirement Benefits and Postemployment Benefits (Schedule of plans with accumulated benefit obiligations in excess of plan assets) (Details) (USD $) In Millions, unless otherwise specified	May 25, 2014	May 26, 2013
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets [Abstract]
Projected benefit obligation	$ 433.1	$ 396.9
Accumulated benefit obligation	375.6	346.6
Plan assets at fair value	0	9.5
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets [Abstract]
Projected benefit obligation	0	0
Accumulated benefit obligation	1,070.0	1,132.9
Plan assets at fair value	517.3	436.9
Postemployment Benefit Plans [Member]
Defined Benefit Plan Pension Plans With Accumulated Benefit Obligations In Excess Of Plan Assets [Abstract]
Projected benefit obligation	0	0
Accumulated benefit obligation	145.3	145.4
Plan assets at fair value	$ 0	$ 0