Fair Value Measurements (Fair Value Hierarchy) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2014	Dec. 31, 2013
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	$ 440,359	$ 5
Derivative Asset, Noncurrent	66,187	9,942
Total Assets	506,546	9,947
Derivative Liability, Current		(53,822)
Derivative Liability, Noncurrent		(3,413)
Total Liabilities		(57,235)
Quoted Prices in Active Markets (Level 1) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	0	0
Derivative Asset, Noncurrent	0	0
Total Assets	0	0
Derivative Liability, Current		0
Derivative Liability, Noncurrent		0
Total Liabilities		0
Significant Other Observable Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	283,238	5
Derivative Asset, Noncurrent	34,862	3,034
Total Assets	318,100	3,039
Derivative Liability, Current		(53,822)
Derivative Liability, Noncurrent		(3,214)
Total Liabilities		(57,036)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	157,121	0
Derivative Asset, Noncurrent	31,325	6,908
Total Assets	188,446	6,908
Derivative Liability, Current		0
Derivative Liability, Noncurrent		(199)
Total Liabilities		$ (199)