Retirement Benefits and Postemployment Benefits (Schedule of fair values of benefit plan assets and their respective levels in fair value heirarchy) (Details) (USD $) In Millions, unless otherwise specified	May 25, 2014	May 26, 2013	May 27, 2012
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	$ 5,611.8	$ 5,066.1	$ 4,353.9
Defined Benefit Pension Plans [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	2,667.5	2,827.0
Defined Benefit Pension Plans [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	1,934.0	1,277.6
Defined Benefit Pension Plans [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	829.4	730.6
Defined Benefit Pension Plans [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0.3	61.2
Defined Benefit Pension Plans [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	180.6	169.7
Defined Benefit Pension Plans [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	2,170.5	2,216.8
Defined Benefit Pension Plans [Member] | Level 1 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	1,305.4	1,439.4
Defined Benefit Pension Plans [Member] | Level 1 [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	586.3	476.6
Defined Benefit Pension Plans [Member] | Level 1 [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	98.2	131.1
Defined Benefit Pension Plans [Member] | Level 1 [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	0
Defined Benefit Pension Plans [Member] | Level 1 [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	180.6	169.7
Defined Benefit Pension Plans [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	2,269.9	1,859.3
Defined Benefit Pension Plans [Member] | Level 2 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	793.9	828.3
Defined Benefit Pension Plans [Member] | Level 2 [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	1,347.7	801.0
Defined Benefit Pension Plans [Member] | Level 2 [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	128.3	169.1
Defined Benefit Pension Plans [Member] | Level 2 [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	60.9
Defined Benefit Pension Plans [Member] | Level 2 [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	0
Defined Benefit Pension Plans [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	1,171.4	990.0	936.9
Defined Benefit Pension Plans [Member] | Level 3 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	568.2	559.3	575.4
Defined Benefit Pension Plans [Member] | Level 3 [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	0
Defined Benefit Pension Plans [Member] | Level 3 [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	602.9	430.4	361.2
Defined Benefit Pension Plans [Member] | Level 3 [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0.3	0.3	0.3
Defined Benefit Pension Plans [Member] | Level 3 [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	0
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	517.3	436.9	358.8
Other Postretirement Benefit Plans [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	236.8	205.3
Other Postretirement Benefit Plans [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	84.3	67.5
Other Postretirement Benefit Plans [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	37.2	23.4
Other Postretirement Benefit Plans [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	152.4	130.9
Other Postretirement Benefit Plans [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	6.6	9.8
Other Postretirement Benefit Plans [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	111.7	121.9
Other Postretirement Benefit Plans [Member] | Level 1 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	86.6	93.1
Other Postretirement Benefit Plans [Member] | Level 1 [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	18.5	17.2
Other Postretirement Benefit Plans [Member] | Level 1 [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	1.8
Other Postretirement Benefit Plans [Member] | Level 1 [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	0
Other Postretirement Benefit Plans [Member] | Level 1 [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	6.6	9.8
Other Postretirement Benefit Plans [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	366.6	280.3
Other Postretirement Benefit Plans [Member] | Level 2 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	129.1	92.0
Other Postretirement Benefit Plans [Member] | Level 2 [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	65.8	50.3
Other Postretirement Benefit Plans [Member] | Level 2 [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	19.3	7.1
Other Postretirement Benefit Plans [Member] | Level 2 [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	152.4	130.9
Other Postretirement Benefit Plans [Member] | Level 2 [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	0
Other Postretirement Benefit Plans [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	39.0	34.7	30.4
Other Postretirement Benefit Plans [Member] | Level 3 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	21.1	20.2	22.0
Other Postretirement Benefit Plans [Member] | Level 3 [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	0
Other Postretirement Benefit Plans [Member] | Level 3 [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	17.9	14.5	8.4
Other Postretirement Benefit Plans [Member] | Level 3 [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	0	0
Other Postretirement Benefit Plans [Member] | Level 3 [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	$ 0	$ 0