Fair Value Measurements (Details) (USD $)	Sep. 30, 2014	Dec. 31, 2013	Sep. 30, 2013
Derivative Asset, Fair Value, Net [Abstract]
Derivative Current Asset, Fair Value	$ 36,000,000	$ 9,300,000
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability	200,000	10,135,000
Derivative, Fair Value, Net [Abstract]
Fair Value, Assets, Level 1 to Level 2 Transfers, Amount	0		0
Level 2 [Member] | Fair Value, Measurements, Recurring [Member]
Derivative, Fair Value, Net [Abstract]
Derivative Asset, Fair Value, Gross Asset (Liability)	35,801,000	(851,000)
Derivative Asset (Liability), Fair Value, Gross Liability (Asset)	0	0
Derivative, Fair Value, Gross Amount Not Offset Against Collateral, Net	35,801,000	(851,000)
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Current Assets [Member]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Current Asset, Fair Value, Gross Asset	22,873,000	2,389,000
Derivative Current Asset, Fair Value, Gross Liability	(2,279,000)	(2,389,000)
Derivative Current Asset, Fair Value	20,594,000	0
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Noncurrent Assets [Member]
Derivative Asset, Fair Value, Net [Abstract]
Derivative Current Asset, Fair Value, Gross Asset	16,328,000	11,709,000
Derivative Current Asset, Fair Value, Gross Liability	(921,000)	(2,425,000)
Derivative Current Asset, Fair Value	15,407,000	9,284,000
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Derivative Liabilities Current [Member]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	(2,414,000)	(12,336,000)
Derivative Liability, Fair Value, Gross Asset	2,279,000	2,389,000
Derivative Liability	(135,000)	(9,947,000)
Level 2 [Member] | Fair Value, Measurements, Recurring [Member] | Other Noncurrent Liabilities [Member]
Derivative Liability, Fair Value, Net [Abstract]
Derivative Liability, Fair Value, Gross Liability	(986,000)	(2,613,000)
Derivative Liability, Fair Value, Gross Asset	921,000	2,425,000
Derivative Liability	$ (65,000)	$ (188,000)