Financial Instruments, Risk Management Activities, and Fair Values (Schedule of swap contract maturities) (Details) (USD $) In Millions, unless otherwise specified	Feb. 24, 2013
Interest Rate Swap Pay Floating [Member]
Derivative [Line Items]
Year Two	$ 300.0
Year Three	0
Year Four	250.0
Total	550.0
Interest Rate Swap Pay Fixed [Member]
Derivative [Line Items]
Year Two	0
Year Three	0
Year Four	0
Total	$ 0