Acquisitions and Divestitures Acquisitions and Divestitures (Components Of Discontinued Operations) (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
Acquisitions and Divestitures [Abstract]
Oil and gas	$ 20,172		$ 21,520		$ 39,765		$ 65,051
Interest and other	0		35		20		4,971
Gain (loss) on disposition of assets, net	0	[1]	(4,574)	[1]	(23)	[1]	645,298	[1]
Total revenues and other income from discontinued operations	20,172		16,981		39,762		715,320
Oil and gas production	1,345		714		2,135		3,937
Depletion, depreciation and amortization	0	[1]	13,544	[1]	0	[1]	27,236	[1]
Exploration and abandonments	1		1,875		86		4,587
General and administrative	12		2,582		1,132		9,397
Accretion of discount on asset retirement obligations	652	[1]	610	[1]	1,304	[1]	1,302	[1]
Interest	0		773		(75)		773
Other	1,581		3,012		1,185		4,214
Total costs and expenses from discontinued operations	3,591		23,110		5,767		51,446
Income from discontinued operations before income taxes	16,581		(6,129)		33,995		663,874
Current tax provision	(3,334)		(12,745)		(8,739)		(26,638)
Deferred tax provision	(1,230)	[1]	15,849	[1]	(2,544)	[1]	(220,379)	[1]
Income from discontinued operations	$ 12,017		$ (3,025)		$ 22,712		$ 416,857

[1] Represents the significant noncash components of discontinued operations.