Fair Value Measurements Fair Value Measurements, Assets (Details) (USD $) In Millions	Sep. 30, 2011	Dec. 31, 2010
Estimate of Fair Value, Fair Value Disclosure [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Restricted Cash	$ 45.5	$ 8.3
Fair Value, Assets Measured on Recurring Basis, Derivative Financial Instruments, Assets	14.5	15.7
Fair Value Assets Measured On Recurring Basis Total Assets	60.0	24.0
Fair Value, Inputs, Level 1 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Restricted Cash	45.5	8.3
Fair Value, Assets Measured on Recurring Basis, Derivative Financial Instruments, Assets	0.5	4.5
Fair Value Assets Measured On Recurring Basis Total Assets	46.0	12.8
Fair Value, Inputs, Level 2 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Restricted Cash	0	0
Fair Value, Assets Measured on Recurring Basis, Derivative Financial Instruments, Assets	3.9	5.3
Fair Value Assets Measured On Recurring Basis Total Assets	3.9	5.3
Fair Value, Inputs, Level 3 [Member]
Fair Value, Assets Measured on Recurring Basis, Financial Statement Captions [Line Items]
Restricted Cash	0	0
Fair Value, Assets Measured on Recurring Basis, Derivative Financial Instruments, Assets	10.1	5.9
Fair Value Assets Measured On Recurring Basis Total Assets	$ 10.1	$ 5.9