Fair Value Measurements Unobservable Input Reconciliation (Details) (USD $) In Millions, unless otherwise specified			12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2011 Commodity Contract [Member] Commodity Contracts, Assets [Member]	Dec. 31, 2012 Fair Value, Inputs, Level 3 [Member]	Dec. 31, 2011 Fair Value, Inputs, Level 3 [Member]
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation [Line Items]
Commodity Contract Assets				$ 0	$ 0
Fair Value, Instruments Classified in Shareholders' Equity Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward]
Level 3 Asset Value, Beginning of Period	53.3	54.3	13.3
Total gains or losses included in other comprehensive income			(5.4)
Settlements			(7.9)
Level 3 Asset Value, End of Period	53.3	54.3	0
Commodity Contracts Liabilities				$ 0	$ 0