Derivative Activities (Gains (Losses) Of Derivative Contacts By Statement Of Operations Location) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2012		Jun. 30, 2011		Jun. 30, 2012		Jun. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instrument	$ 98,875		$ 14,446		$ 83,288		$ (45,306)
Unrealized gain (loss) on derivative instrument					65,624		(3,192)
Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instrument	103,904	[1]	26,299	[1]	90,206	[1]	(33,997)	[1]
Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instrument	(5,029)	[2]	(11,853)	[2]	(6,918)	[2]	(11,309)	[2]
Realized Gain (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instrument	11,896		(43,109)		17,664		(42,114)
Realized Gain (Loss) [Member] | Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instrument	14,222	[1]	(42,161)	[1]	22,293	[1]	(40,852)	[1]
Realized Gain (Loss) [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instrument	(2,326)	[2]	(948)	[2]	(4,629)	[2]	(1,262)	[2]
Unrealized Gain (Loss) [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivative instrument	86,979		57,555		65,624		(3,192)
Unrealized Gain (Loss) [Member] | Commodity Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on derivative instrument	89,682		68,460		67,913		6,855
Unrealized gain (loss) on derivative instrument	89,682	[1]	68,460	[1]	67,913	[1]	6,855	[1]
Unrealized Gain (Loss) [Member] | Interest Rate Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gain (loss) on derivative instrument	$ (2,703)	[2]	$ (10,905)	[2]	$ (2,289)	[2]	$ (10,047)	[2]

[1] Gain (loss) on commodity derivative contracts is located in other income (expense) in the consolidated statement of operations.

[2] Gain (loss) on interest rate derivatives contracts is recorded as part of interest expense and is located in other income (expense) in the consolidated statement of operations.