Condensed Consolidating Financial Statements (Schedule Of Condensed Consolidating Statement Of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Oil and natural gas	$ 182,966	$ 150,332	$ 381,438	$ 288,555
Oil and natural gas production	23,191	15,883	49,587	34,748
Gathering and transportation	26,038	23,408	50,651	47,884
Depletion, depreciation and amortization	67,253	47,388	136,528	88,696
Impairment of oil and natural gas properties	0	0	0	10,707
Accretion of discount on asset retirement obligations	695	556	1,376	1,246
General and administrative	19,504	26,574	36,842	44,558
Other operating items	2,973	2,640	5,719	(182,242)
Total costs and expenses	139,654	116,449	280,703	45,597
Operating income (loss)	43,312	33,883	100,735	242,958
Interest expense, net	(25,968)	(15,105)	(46,132)	(35,297)
Gain (loss) on derivative financial instruments	(14,718)	55,246	(57,740)	11,732
Other income	77	158	123	246
Equity income (loss)	(410)	11,416	701	24,079
Net earnings (loss) from consolidated subsidiaries	0	0	0	0
Total other income (expense)	(41,019)	51,715	(103,048)	760
Income (loss) before income taxes	2,293	85,598	(2,313)	243,718
Income tax expense	0	0	0	0
Net income (loss)	2,293	85,598	(2,313)	243,718
Resources [Member]
Oil and natural gas	306	74	3,296	8,120
Oil and natural gas production	76	71	375	2,283
Gathering and transportation	0	0	0	0
Depletion, depreciation and amortization	727	1,192	1,884	3,799
Impairment of oil and natural gas properties				0
Accretion of discount on asset retirement obligations	4	4	9	54
General and administrative	962	9,640	727	10,293
Other operating items	(12)	745	(16)	(25,229)
Total costs and expenses	1,757	11,652	2,979	(8,800)
Operating income (loss)	(1,451)	(11,578)	317	16,920
Interest expense, net	(25,301)	(14,298)	(44,796)	(34,175)
Gain (loss) on derivative financial instruments	(13,958)	51,495	(54,637)	11,693
Other income	59	82	152	129
Equity income (loss)	0	0	0	0
Net earnings (loss) from consolidated subsidiaries	42,944	59,897	96,651	249,151
Total other income (expense)	3,744	97,176	(2,630)	226,798
Income (loss) before income taxes	2,293	85,598	(2,313)	243,718
Income tax expense	0	0	0	0
Net income (loss)	2,293	85,598	(2,313)	243,718
Guarantor Subsidiaries [Member]
Oil and natural gas	169,795	137,318	351,856	261,792
Oil and natural gas production	18,196	10,559	39,617	24,664
Gathering and transportation	24,899	22,500	48,348	46,507
Depletion, depreciation and amortization	61,840	42,761	125,507	80,289
Impairment of oil and natural gas properties				10,707
Accretion of discount on asset retirement obligations	522	396	1,032	945
General and administrative	17,949	16,421	34,795	33,384
Other operating items	2,977	1,904	5,731	(157,000)
Total costs and expenses	126,383	94,541	255,030	39,496
Operating income (loss)	43,412	42,777	96,826	222,296
Interest expense, net	0	0	0	0
Gain (loss) on derivative financial instruments	0	455	0	(235)
Other income	14	76	(37)	115
Equity income (loss)	0	0	0	0
Net earnings (loss) from consolidated subsidiaries	0	0	0	0
Total other income (expense)	14	531	(37)	(120)
Income (loss) before income taxes	43,426	43,308	96,789	222,176
Income tax expense	0	0	0	0
Net income (loss)	43,426	43,308	96,789	222,176
Non-Guarantor Subsidiaries [Member]
Oil and natural gas	12,865	12,940	26,286	18,643
Oil and natural gas production	4,919	5,253	9,595	7,801
Gathering and transportation	1,139	908	2,303	1,377
Depletion, depreciation and amortization	4,686	3,435	9,137	4,608
Impairment of oil and natural gas properties				0
Accretion of discount on asset retirement obligations	169	156	335	247
General and administrative	593	513	1,320	881
Other operating items	8	(9)	4	(13)
Total costs and expenses	11,514	10,256	22,694	14,901
Operating income (loss)	1,351	2,684	3,592	3,742
Interest expense, net	(667)	(807)	(1,336)	(1,122)
Gain (loss) on derivative financial instruments	(760)	3,296	(3,103)	274
Other income	4	0	8	2
Equity income (loss)	(410)	11,416	701	24,079
Net earnings (loss) from consolidated subsidiaries	0	0	0	0
Total other income (expense)	(1,833)	13,905	(3,730)	23,233
Income (loss) before income taxes	(482)	16,589	(138)	26,975
Income tax expense	0	0	0	0
Net income (loss)	(482)	16,589	(138)	26,975
Eliminations [Member]
Oil and natural gas	0	0	0	0
Oil and natural gas production	0	0	0	0
Gathering and transportation	0	0	0	0
Depletion, depreciation and amortization	0	0	0	0
Impairment of oil and natural gas properties				0
Accretion of discount on asset retirement obligations	0	0	0	0
General and administrative	0	0	0	0
Other operating items	0	0	0	0
Total costs and expenses	0	0	0	0
Operating income (loss)	0	0	0	0
Interest expense, net	0	0	0	0
Gain (loss) on derivative financial instruments	0	0	0	0
Other income	0	0	0	0
Equity income (loss)	0	0	0	0
Net earnings (loss) from consolidated subsidiaries	(42,944)	(59,897)	(96,651)	(249,151)
Total other income (expense)	(42,944)	(59,897)	(96,651)	(249,151)
Income (loss) before income taxes	(42,944)	(59,897)	(96,651)	(249,151)
Income tax expense	0	0	0	0
Net income (loss)	$ (42,944)	$ (59,897)	$ (96,651)	$ (249,151)