Derivatives And Risk Management (Balance Sheet Classification Of Derivative Financial Instruments) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Derivative [Line Items]
Derivative assets	$ 47,153	$ 78,503
Derivative liabilities	119,378	40,490
Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative assets	1,362	20,631
Derivative liabilities	32,971	3,884
Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Derivative Assets [Member]
Derivative [Line Items]
Derivative assets	1,362	20,631
Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	32,971	3,884
Not Designated as Hedging Instrument [Member]
Derivative [Line Items]
Derivative assets	45,791	57,872
Derivative liabilities	86,407	36,606
Not Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Derivative Assets [Member]
Derivative [Line Items]
Derivative assets	390	37,382
Not Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Other Long-Term Assets [Member]
Derivative [Line Items]
Derivative assets	30,245
Not Designated as Hedging Instrument [Member] | Fixed Price Swaps [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	16,022	185
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Derivative Assets [Member]
Derivative [Line Items]
Derivative assets	9,692	12,858
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Other Long-Term Assets [Member]
Derivative [Line Items]
Derivative assets		107
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	7,808	1,501
Not Designated as Hedging Instrument [Member] | Basis Swaps [Member] | Other Long-Term Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	603
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Other Long-Term Assets [Member]
Derivative [Line Items]
Derivative assets	5,464	7,525
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	2,177	1,520
Not Designated as Hedging Instrument [Member] | Interest Rate Swaps [Member] | Other Long-Term Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	2,495	3,012
Not Designated as Hedging Instrument [Member] | Fixed Price Call Options [Member] | Other Current Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	17,273
Not Designated as Hedging Instrument [Member] | Fixed Price Call Options [Member] | Other Long-Term Liabilities [Member]
Derivative [Line Items]
Derivative liabilities	$ 40,029	$ 30,388