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		May 29, 2016		May 31, 2015		May 25, 2014
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		$ 5,539.9		$ 5,758.5		$ 5,611.8
Defined Benefit Pension Plans [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[1]	2,945.4		3,187.6
Defined Benefit Pension Plans [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[2]	1,649.6		1,644.8
Defined Benefit Pension Plans [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[3]	749.4		739.1
Defined Benefit Pension Plans [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[4]	0.4		0.4
Defined Benefit Pension Plans [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		195.1		186.6
Defined Benefit Pension Plans [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		2,836.2		2,431.6
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]	1,543.7		1,634.4
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	[2]	903.8		486.3
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	[3]	193.6		124.3
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	[4]	0.0		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		195.1		186.6
Defined Benefit Pension Plans [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		1,850.3		2,285.5
Defined Benefit Pension Plans [Member] | Level 2 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[1]	943.7		1,010.3
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	[2]	745.8		1,158.5
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	[3]	160.8		116.7
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	[4]	0.0		0.0
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		0.0
Defined Benefit Pension Plans [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		853.4		1,041.4		1,171.4
Defined Benefit Pension Plans [Member] | Level 3 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		458.0	[1]	542.9	[1]	568.2
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	[2]	0.0		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		395.0	[3]	498.1	[3]	602.9
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		0.4	[4]	0.4	[4]	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		0.0
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		602.4		582.8		517.3
Other Postretirement Benefit Plans [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[1]	276.4		278.3
Other Postretirement Benefit Plans [Member] | Fixed income [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[2]	101.4		87.7
Other Postretirement Benefit Plans [Member] | Real asset investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[3]	44.4		42.5
Other Postretirement Benefit Plans [Member] | Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[4]	171.3		168.9
Other Postretirement Benefit Plans [Member] | Cash and accruals [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		8.9		5.4
Other Postretirement Benefit Plans [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		155.8		153.6
Other Postretirement Benefit Plans [Member] | Level 1 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[1]	128.9		134.0
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	[2]	18.0		14.0
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	[3]	0.0		0.2
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	[4]	0.0		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		8.9		5.4
Other Postretirement Benefit Plans [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		409.4		388.9
Other Postretirement Benefit Plans [Member] | Level 2 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets	[1]	124.1		120.6
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	[2]	83.4		73.7
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	[3]	30.6		25.7
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	[4]	171.3		168.9
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		0.0
Other Postretirement Benefit Plans [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		37.2		40.3		39.0
Other Postretirement Benefit Plans [Member] | Level 3 [Member] | Equity [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan Fair Value Of Plan Assets		23.4	[1]	23.7	[1]	21.1
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	[2]	0.0		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		13.8	[3]	16.6	[3]	$ 17.9
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	[4]	0.0		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		$ 0.0

[1] Primarily publicly traded common stock and private equity partnerships for purposes of total return and to maintain equity exposure consistent with policy allocations. Investments include: United States and international equity securities, mutual funds, and equity futures valued at closing prices from national exchanges; and commingled funds, privately held securities, and private equity partnerships valued at unit values or net asset value s provided by the investment managers, which are based on the fair value of the underlying investments. Various methods are used to determine fair values and may include the cost of the investment, most recent financing, and expected cash flows. For some o f these investments, realization of the estimated fair value is dependent upon transactions between willing sellers and buyers.

[2] Primarily government and corporate debt securities and futures for purposes of total return, managing fixed income exposure to policy allocations, and managing duration targets. Investments include: fixed income securities and bond futures generally valued at closing prices from national exchanges, fixed income pricing models, and independent financial analysts; and fixed inco me commingled funds valued at unit values provided by the investment managers, which are based on the fair value of the underlying investments.

[3] Publicly traded common stock and limited partnerships in the energy and real estate sectors for purposes o f total return. Investments include: energy and real estate securities generally valued at closing prices from national exchanges; and commingled funds, private securities, and limited partnerships valued at unit values or net asset values provided by the investment managers, which are generally based on the fair value of the underlying investments.

[4] Global balanced fund of equity, fixed income, and real estate securities for purposes of meeting Canadian pension plan asset allocation policies, and insur ance and annuity contracts to provide a stable stream of income for retirees and to fund postretirement medical benefits. Fair values are derived from unit values provided by the investment managers, which are generally based on the fair value of the under lying investments and contract fair values from the providers.