Supplemental Condensed Consolidating Financial Information (Supplemental Condensed Consolidating Statement of Operations) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Oil and natural gas	$ 183,114	$ 86,645	$ 547,099	$ 284,666
Other	878	23	3,329	68
Total Revenue	183,992	86,668	550,428	284,734
Lease operating	42,291	24,995	126,663	62,067
Transportation	974	160	2,317	410
Exploration expenditures and dry hole costs	5,146	966	13,609	17,862
Impairments	12	498	2,183	6,206
Depreciation, depletion and amortization	53,989	27,106	153,847	78,932
Accretion of liability for asset retirement obligations	6,266	3,472	18,464	10,031
General and administrative	6,426	5,995	20,927	16,993
Taxes, other than on earnings	3,285	3,189	8,884	9,834
Gain on sale of assets	(1,745)		(28,601)
Other	26,534	998	33,077	4,616
Total costs and expenses	143,178	67,379	351,370	206,951
Income from operations	40,814	19,289	199,058	77,783
Interest income	64	40	91	128
Interest expense	(13,177)	(5,114)	(39,370)	(15,081)
Gain (loss) on derivative instruments	(30,012)	(22,108)	(7,033)	(11,865)
Total other income (expense)	(43,125)	(27,182)	(46,312)	(26,818)
Income (loss) before provision for income taxes	(2,311)	(7,893)	152,746	50,965
Current income tax expense	(25)	126	(175)	(174)
Deferred income tax expense	1,052	5,520	(55,239)	(16,134)
Total provision for income taxes	1,027	5,646	(55,414)	(16,308)
Net income (loss)	(1,284)	(2,247)	97,332	34,657
Parent Company [Member]
Oil and natural gas	159,902	65,339	483,488	204,921
Other	127	3,750	536	11,254
Total Revenue	160,029	69,089	484,024	216,175
Lease operating	35,995	19,160	107,200	47,060
Transportation	974	160	2,298	406
Exploration expenditures and dry hole costs	5,145	977	9,936	17,854
Impairments	12	498	2,183	6,206
Depreciation, depletion and amortization	48,451	23,376	137,810	64,088
Accretion of liability for asset retirement obligations	5,077	2,185	15,027	6,359
General and administrative	6,426	5,864	20,927	16,630
Taxes, other than on earnings	225	510	848	1,004
Gain on sale of assets	(1,745)		(28,139)
Other	26,407	997	32,208	4,616
Total costs and expenses	126,967	53,727	300,298	164,223
Income from operations	33,062	15,362	183,726	51,952
Interest income	64	40	91	128
Interest expense	(13,177)	(5,114)	(39,370)	(15,081)
Gain (loss) on derivative instruments	(30,012)	(22,108)	(7,033)	(11,865)
Income (loss) from equity investments	4,930	2,643	9,751	16,377
Total other income (expense)	(38,195)	(24,539)	(36,561)	(10,441)
Income (loss) before provision for income taxes	(5,133)	(9,177)	147,165	41,511
Current income tax expense	(25)	126	(175)	(174)
Deferred income tax expense	3,874	6,804	(49,658)	(6,680)
Total provision for income taxes	3,849	6,930	(49,833)	(6,854)
Net income (loss)	(1,284)	(2,247)	97,332	34,657
Guarantor Subsidiaries [Member]
Oil and natural gas	23,212	21,306	63,611	79,745
Other	751	23	2,793	64
Total Revenue	23,963	21,329	66,404	79,809
Lease operating	6,296	5,835	19,463	15,007
Transportation			19	4
Exploration expenditures and dry hole costs	1	(11)	3,673	8
Depreciation, depletion and amortization	5,538	3,730	16,037	14,844
Accretion of liability for asset retirement obligations	1,189	1,287	3,437	3,672
General and administrative		3,881		11,613
Taxes, other than on earnings	3,060	2,679	8,036	8,830
Gain on sale of assets			(462)
Other	127	1	869
Total costs and expenses	16,211	17,402	51,072	53,978
Income from operations	7,752	3,927	15,332	25,831
Income (loss) before provision for income taxes	7,752	3,927	15,332	25,831
Deferred income tax expense	(2,822)	(1,284)	(5,581)	(9,454)
Total provision for income taxes	(2,822)	(1,284)	(5,581)	(9,454)
Net income (loss)	4,930	2,643	9,751	16,377
Consolidation, Eliminations [Member]
Other		(3,750)		(11,250)
Total Revenue		(3,750)		(11,250)
General and administrative		(3,750)		(11,250)
Total costs and expenses		(3,750)		(11,250)
Income (loss) from equity investments	(4,930)	(2,643)	(9,751)	(16,377)
Total other income (expense)	(4,930)	(2,643)	(9,751)	(16,377)
Income (loss) before provision for income taxes	(4,930)	(2,643)	(9,751)	(16,377)
Net income (loss)	$ (4,930)	$ (2,643)	$ (9,751)	$ (16,377)