Derivatives And Fair Value Measurements (Changes In Level 3 Fair Values) (Details) (Fair Value Inputs, Level 3 [Member], USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Balance at beginning of period	$ (9,873)	$ 45,345	$ (4,931)	$ 150,989
Unrealized gain (loss) on derivatives	24,080	(51,685)	24,618	16,160
Transfers out of Level 3			0	(153,418)
Unrealized gains reported in OCI	0	409	0	33,306
Balance at end of period	10,905	(13,626)	10,905	(13,626)
Total gains included in net derivative gains attributable to the change in unrealized gains related to assets still held at the reporting date	24,026	(51,685)	26,788	(16,160)
Production Revenue [Member]
Settlements	0	(825)	0	(5,600)
Other Revenue [Member]
Settlements	$ (3,302)	$ (6,870)	$ (8,782)	$ (22,743)