Fair Value Measurements (Fair Value Hierarchy) (Details) (USD $) In Thousands, unless otherwise specified	Dec. 31, 2013	Dec. 31, 2012
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	$ 5	$ 19,477
Derivative Asset, Noncurrent	9,942	36
Total Derivative Assets	9,947	19,513
Derivative Liability, Current	(53,822)	(2,659)
Derivative Liability, Noncurrent	(3,413)	(23,781)
Total Derivative Liabilities	(57,235)	(26,440)
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 Derivative Assets	0	0
Derivative Liability, Current	0	0
Derivative Liability, Noncurrent	0	0
Total Derivative Liabilities	0	0
Significant Other Observable Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	5	19,477
Derivative Asset, Noncurrent	3,034	36
Total Derivative Assets	3,039	19,513
Derivative Liability, Current	(53,822)	(2,659)
Derivative Liability, Noncurrent	(3,214)	(23,781)
Total Derivative Liabilities	(57,036)	(26,440)
Significant Unobservable Inputs (Level 3) [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative Asset, Current	0	0
Derivative Asset, Noncurrent	6,908	0
Total Derivative Assets	6,908	0
Derivative Liability, Current	0	0
Derivative Liability, Noncurrent	(199)	0
Total Derivative Liabilities	$ (199)	$ 0