Retirement Benefits and Postemployment Benefits (Schedule of estimated benefit payments) (Details) (USD $) In Millions, unless otherwise specified	May 26, 2013
Defined Benefit Plan Estimated Future Benefit Payments [Abstract]
Medicare Subsidy Receipts, Next Twelve Months	$ 4.7
Medicare Subsidy Receipts, Year Two	5.2
Medicare Subsidy Receipts, Year Three	5.6
Medicare Subsidy Receipts, Year Four	6.1
Medicare Subsidy Receipts, Year Five	6.5
Medicare Subsidy Receipts, Five Fiscal Years Thereafter	28.5
Defined Benefit Pension Plans [Member]
Defined Benefit Plan Estimated Future Benefit Payments [Abstract]
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	236.3
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	243.6
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	251.6
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	260.6
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	270.1
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	1,512.3
Other Postretirement Benefit Plans [Member]
Defined Benefit Plan Estimated Future Benefit Payments [Abstract]
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	56.8
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	60.4
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	62.4
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	63.8
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	66.7
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	371.3
Postemployment Benefit Plans [Member]
Defined Benefit Plan Estimated Future Benefit Payments [Abstract]
Defined Benefit Plan, Expected Future Benefit Payments, Next Twelve Months	18.8
Defined Benefit Plan, Expected Future Benefit Payments, Year Two	17.4
Defined Benefit Plan, Expected Future Benefit Payments, Year Three	16.3
Defined Benefit Plan, Expected Future Benefit Payments, Year Four	15.3
Defined Benefit Plan, Expected Future Benefit Payments, Year Five	14.7
Defined Benefit Plan, Expected Future Benefit Payments, Five Fiscal Years Thereafter	$ 66.4