Financial Derivative Instruments Financial Derivative Instruments - Risk and Collateral (Details 4) (USD $)	Sep. 30, 2014	Dec. 31, 2013
Credit Derivatives [Line Items]
Derivative Liability, Collateral, Right to Reclaim Cash, Offset	$ 7,000,000	$ 0
Other accrued liabilities | Derivatives not designated as hedging instruments | Fuel derivative contracts
Credit Derivatives [Line Items]
Derivative Assets (Liabilities), at Fair Value, Net	$ (18,670,000)