Fair Value Measurements (Summary Assets And Liabilities Measured At Fair Value On Recurring Basis) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Quoted Prices in Active Markets for Identical Assets, Level 1 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets
Derivative liabilities
Total
Significant Observable Inputs, Level 2 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	37,461	65,538
Derivative liabilities	(53,665)	(8,601)
Total	(16,204)	56,937
Significant Unobservable Inputs, Level 3 [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	9,692	12,965
Derivative liabilities	(65,713)	(31,889)
Total	(56,021)	(18,924)
Fair Value [Member]
Fair Value, Assets and Liabilities Measured on Recurring and Nonrecurring Basis [Line Items]
Derivative assets	47,153	78,503
Derivative liabilities	(119,378)	(40,490)
Total	$ (72,225)	$ 38,013