Retirement Benefits and Postemployment Benefits (Schedule of asset allocations for benefit plans) (Details)	May 26, 2013	May 27, 2012
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Weighted-Average Asset Allocations	100.00%	100.00%
Fixed income	27.50%	28.60%
Real assets	14.50%	13.70%
Defined Benefit Pension Plans [Member] | United States Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Weighted-Average Asset Allocations	29.50%	28.70%
Defined Benefit Pension Plans [Member] | International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Weighted-Average Asset Allocations	17.30%	15.70%
Defined Benefit Pension Plans [Member] | Private Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Weighted-Average Asset Allocations	11.20%	13.30%
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Weighted-Average Asset Allocations	100.00%	100.00%
Fixed income	28.90%	30.30%
Real assets	5.40%	5.20%
Other Postretirement Benefit Plans [Member] | United States Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Weighted-Average Asset Allocations	39.40%	38.40%
Other Postretirement Benefit Plans [Member] | International Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Weighted-Average Asset Allocations	21.60%	19.90%
Other Postretirement Benefit Plans [Member] | Private Equities [Member]
Defined Benefit Plan Disclosure [Line Items]
Defined Benefit Plan, Weighted-Average Asset Allocations	4.70%	6.20%