Supplemental Oil And Gas Disclosures (Results Of Operations For Oil And Gas Producing Activities) (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010		Dec. 31, 2009
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Revenues	$ 696,607		$ 425,369		$ 385,338
Production (lifting) costs	180,243		135,685		119,836
Hurricane repair expense	(4,838)		4,699		(23,332)
Exploration expenses	10,914	[1]	8,276	[1]	24,383	[1]
Depreciation, depletion, amortization and accretion	219,915		235,290		169,256
Proved property impairment charges and other	133,406	[2]	182,133	[2]	73,407	[2]
Gain on sale or acquisition of oil and gas properties	(4,531)		(6,246)		(1,949)
Gain on oil and gas derivative contracts			(1,088)		(89,485)
Selling and administrative expenses	31,562		26,826		21,554
Pretax income (loss) from producing activities	129,936		(160,206)		91,668
Income tax expense (benefit)	35,858		(62,954)		23,252
Results of oil and gas producing activities	94,078	[3]	(97,252)	[3]	68,416	[3]
United States [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Revenues	696,607		425,369		384,375
Production (lifting) costs	176,269		131,156		117,565
Hurricane repair expense	(4,838)		4,699		(23,332)
Exploration expenses	10,914	[1]	8,276	[1]	24,383	[1]
Depreciation, depletion, amortization and accretion	219,915		235,243		167,812
Proved property impairment charges and other	113,439	[2]	177,138	[2]	73,407	[2]
Gain on sale or acquisition of oil and gas properties	(4,531)		(287)		(1,949)
Gain on oil and gas derivative contracts			(1,088)		(89,485)
Selling and administrative expenses	31,455		26,714		21,495
Pretax income (loss) from producing activities	153,984		(156,482)		94,479
Income tax expense (benefit)	45,233		(62,526)		24,280
Results of oil and gas producing activities	108,751	[3]	(93,956)	[3]	70,199	[3]
United Kingdom [Member]
Results of Operations for Oil and Gas Producing Activities, by Geographic Area [Line Items]
Revenues					963
Production (lifting) costs	3,974		4,529		2,271
Depreciation, depletion, amortization and accretion			47		1,444
Proved property impairment charges and other	19,967	[2]	4,995	[2]
Gain on sale or acquisition of oil and gas properties			(5,959)
Selling and administrative expenses	107		112		59
Pretax income (loss) from producing activities	(24,048)		(3,724)		(2,811)
Income tax expense (benefit)	(9,375)		(428)		(1,028)
Results of oil and gas producing activities	$ (14,673)	[3]	$ (3,296)	[3]	$ (1,783)	[3]

[1] See Note 5 for additional information related to the components of our exploration costs, including impairment charges for expiring unproved leases.

[2] Other amounts represent additional asset retirement expense recorded upon completion of a field's abandonment.

[3] Excludes net interest expense and other.