Derivatives (Fair Value Of Derivative Instruments And Locations In Balance Sheets) (Details) (USD $) In Thousands	Sep. 30, 2011	Dec. 31, 2010
Current derivative assets	$ 41,257	$ 5,568
Non-current derivative assets	23,989	2,537
Total derivatives assets	65,246	8,105
Current derivative liabilities	552	14,446
Non-current derivative liabilities	0	4,359
Total derivative liabilities	552	18,805
Interest Rate Swaps [Member] | Designated As Hedging Instrument [Member]
Current derivative liabilities	0	1,139
Non-current derivative liabilities	0	475
Designated As Hedging Instrument [Member]
Total derivatives assets	65,246	7,628
Total derivative liabilities	342	18,664
Designated As Hedging Instrument [Member] | Commodity Contract [Member]
Current derivative assets	41,257	5,091
Non-current derivative assets	23,989	2,537
Current derivative liabilities	342	13,166
Non-current derivative liabilities	0	3,884
Not Designated As Hedging Instrument [Member]
Total derivatives assets	0	477
Total derivative liabilities	210	141
Not Designated As Hedging Instrument [Member] | Commodity Contract [Member]
Current derivative assets	0	477
Not Designated As Hedging Instrument [Member] | Commodity Basis Swap [Member]
Current derivative liabilities	$ 210	$ 141