Condensed Consolidating Financial Statements (Schedule Of Condensed Consolidating Statement Of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Oil and natural gas	$ 134,848	$ 161,228
Oil and natural gas production	29,989	24,644
Gathering and transportation	26,423	17,286
Depreciation, depletion and amortization	89,582	67,930
Write-down of oil and natural gas properties	275,864	0
Accretion of discount on asset retirement obligations	947	857
General and administrative	21,505	23,423
Other operating items	1,625	2,457
Total costs and expenses	445,935	136,597
Operating income (loss)	(311,087)	24,631
Interest expense	(16,764)	(14,816)
Gain on derivative financial instruments	53,865	3,421
Other income (expense)	243	160
Equity method income	(7,906)	8,545
Equity in earnings of subsidiaries	0	0
Total other income (expense)	29,438	(2,690)
Income (loss) before income taxes	(281,649)	21,941
Income tax expense	0	0
Net income (loss)	(281,649)	21,941
Resources [Member]
Oil and natural gas	23,273	23,386
Oil and natural gas production	5,125	4,287
Gathering and transportation	0	0
Depreciation, depletion and amortization	(6,892)	6,566
Write-down of oil and natural gas properties	0
Accretion of discount on asset retirement obligations	126	101
General and administrative	3,775	4,716
Other operating items	42	2,616
Total costs and expenses	2,176	18,286
Operating income (loss)	21,097	5,100
Interest expense	(16,764)	(13,564)
Gain on derivative financial instruments	49,223	3,601
Other income (expense)	36	84
Equity method income	0	0
Equity in earnings of subsidiaries	(335,241)	26,720
Total other income (expense)	(302,746)	16,841
Income (loss) before income taxes	(281,649)
Income tax expense	0
Net income (loss)	(281,649)	21,941
Guarantor Subsidiaries [Member]
Oil and natural gas	111,575	137,842
Oil and natural gas production	24,864	20,357
Gathering and transportation	26,423	17,286
Depreciation, depletion and amortization	96,474	60,993
Write-down of oil and natural gas properties	275,864
Accretion of discount on asset retirement obligations	821	756
General and administrative	17,730	18,707
Other operating items	1,583	553
Total costs and expenses	443,759	118,652
Operating income (loss)	(332,184)	19,190
Interest expense	0	(1,252)
Gain on derivative financial instruments	4,642	(180)
Other income (expense)	207	76
Equity method income	0	0
Equity in earnings of subsidiaries	0	0
Total other income (expense)	4,849	(1,356)
Income (loss) before income taxes	(327,335)
Income tax expense	0
Net income (loss)	(327,335)	17,834
Non-Guarantor Subsidiaries [Member]
Oil and natural gas	0	0
Oil and natural gas production	0	0
Gathering and transportation	0	0
Depreciation, depletion and amortization	0	371
Write-down of oil and natural gas properties	0
Accretion of discount on asset retirement obligations	0	0
General and administrative	0	0
Other operating items	0	(712)
Total costs and expenses	0	(341)
Operating income (loss)	0	341
Interest expense	0	0
Gain on derivative financial instruments	0	0
Other income (expense)	0	0
Equity method income	(7,906)	8,545
Equity in earnings of subsidiaries	0	0
Total other income (expense)	(7,906)	8,545
Income (loss) before income taxes	(7,906)
Income tax expense	0
Net income (loss)	(7,906)	8,886
Eliminations [Member]
Oil and natural gas	0	0
Oil and natural gas production	0	0
Gathering and transportation	0	0
Depreciation, depletion and amortization	0	0
Write-down of oil and natural gas properties	0
Accretion of discount on asset retirement obligations	0	0
General and administrative	0	0
Other operating items	0	0
Total costs and expenses	0	0
Operating income (loss)	0	0
Interest expense	0	0
Gain on derivative financial instruments	0	0
Other income (expense)	0	0
Equity method income	0	0
Equity in earnings of subsidiaries	335,241	(26,720)
Total other income (expense)	335,241	(26,720)
Income (loss) before income taxes	335,241
Income tax expense	0
Net income (loss)	$ 335,241	$ (26,720)