Guarantor Financial Statements (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Operating revenue:
Oil production	$ 182,181	$ 175,357	$ 383,939	$ 327,352
Gas production	28,146	47,884	57,003	89,044
Natural gas liquids production	9,866	10,231	23,318	16,230
Other operational income	952	864	1,842	1,749
Derivative income, net	5,416	1,398	4,931
Total operating revenue	226,561	235,734	471,033	434,375
Operating expenses:
Lease operating expenses	51,555	45,608	96,035	83,895
Transportation, processing and gathering expenses	5,492	2,728	9,149	4,548
Other operational expense	71	136	113	798
Production taxes	2,358	1,801	5,736	4,336
Depreciation, depletion, amortization	87,133	72,646	171,708	140,315
Accretion expense	8,255	7,717	16,521	15,434
Salaries, general and administrative	13,143	10,610	26,848	22,343
Incentive compensation expense	2,398	2,333	3,840	5,017
Derivative expense, net				782
Total operating expenses	170,405	143,579	329,950	277,468
Income from operations	56,156	92,155	141,083	156,907
Other (income) expenses:
Interest expense	7,684	1,980	13,415	5,091
Interest income	(79)	(53)	(110)	(147)
Other income	(366)	(563)	(786)	(1,127)
Other expense		69		193
Loss on early extinguishment of debt		607		607
Total other expenses	7,239	2,040	12,519	4,617
Net income before income taxes	48,917	90,115	128,564	152,290
Provision (benefit) for income taxes:
Current	(665)	(2,362)	569	(2,362)
Deferred	19,035	35,281	46,474	57,664
Total income taxes	18,370	32,919	47,043	55,302
Net income	30,547	57,196	81,521	96,988
Comprehensive income (loss)	93,749	93,308	122,658	100,626
Parent [Member]
Operating revenue:
Oil production	6,813	732	13,047	1,518
Gas production	5,865	4,303	11,496	5,583
Natural gas liquids production	1,710		5,574
Other operational income	762	587	1,456	1,309
Total operating revenue	15,150	5,622	31,573	8,410
Operating expenses:
Lease operating expenses	6,318	390	11,222	746
Transportation, processing and gathering expenses	1,710		4,198
Other operational expense	47	93	89	93
Production taxes	507	245	1,670	392
Depreciation, depletion, amortization	15,071	(24)	26,548	5,918
Accretion expense	137	4	285	8
Salaries, general and administrative	14,190	10,562	26,844	22,293
Incentive compensation expense	2,398	2,333	3,840	5,017
Total operating expenses	40,378	13,603	74,696	34,467
Income from operations	(25,228)	(7,981)	(43,123)	(26,057)
Other (income) expenses:
Interest expense	7,672	1,979	13,518	5,010
Interest income	(74)	(53)	(104)	(141)
Other income	(4)	(13)	(23)	(13)
Other expense		69		192
Loss on early extinguishment of debt		607		607
(Income) loss from investment in subsidiaries	(52,313)	(63,621)	(118,450)	(116,944)
Total other expenses	(44,719)	(61,032)	(105,059)	(111,289)
Net income before income taxes	19,491	53,051	61,936	85,232
Provision (benefit) for income taxes:
Current	(665)	(9)	569	(9)
Deferred	(10,391)	(4,136)	(20,154)	(11,747)
Total income taxes	(11,056)	(4,145)	(19,585)	(11,756)
Net income	30,547	57,196	81,521	96,988
Comprehensive income (loss)	93,749	93,308	122,658	100,626
Guarantor Subsidiary [Member]
Operating revenue:
Oil production	175,368	174,625	370,892	325,834
Gas production	22,281	43,581	45,507	83,461
Natural gas liquids production	8,156	10,231	17,744	16,230
Other operational income	77	104	140	85
Derivative income, net	5,416	1,398	4,931
Total operating revenue	211,298	229,939	439,214	425,610
Operating expenses:
Lease operating expenses	45,443	45,218	84,830	83,149
Transportation, processing and gathering expenses	3,782	2,728	4,951	4,548
Other operational expense	24	40	24	702
Production taxes	1,851	1,556	4,066	3,944
Depreciation, depletion, amortization	71,969	72,426	144,969	133,936
Accretion expense	8,033	7,622	16,065	15,244
Salaries, general and administrative	(1,047)	48	4	50
Derivative expense, net				782
Total operating expenses	130,055	129,638	254,909	242,355
Income from operations	81,243	100,301	184,305	183,255
Other (income) expenses:
Interest expense	12	1	(103)	81
Interest income	(5)		(6)	(6)
Other income	(362)	(547)	(763)	(1,114)
Other expense				1
(Income) loss from investment in subsidiaries	(140)	162	99	291
Total other expenses	(495)	(384)	(773)	(747)
Net income before income taxes	81,738	100,685	185,078	184,002
Provision (benefit) for income taxes:
Current		(2,353)		(2,353)
Deferred	29,426	39,417	66,628	69,411
Total income taxes	29,426	37,064	66,628	67,058
Net income	52,312	63,621	118,450	116,944
Comprehensive income (loss)	52,312	63,621	118,450	116,944
Non-Guarantor Subsidiaries [Member]
Operating revenue:
Other operational income	113	173	246	355
Total operating revenue	113	173	246	355
Operating expenses:
Lease operating expenses	(206)		(17)
Other operational expense		3		3
Depreciation, depletion, amortization	93	244	191	461
Accretion expense	85	91	171	182
Total operating expenses	(28)	338	345	646
Income from operations	141	(165)	(99)	(291)
Other (income) expenses:
Other income		(3)
Total other expenses		(3)
Net income before income taxes	141	(162)	(99)	(291)
Provision (benefit) for income taxes:
Net income	141	(162)	(99)	(291)
Comprehensive income (loss)	141	(162)	(99)	(291)
Eliminations [Member]
Other (income) expenses:
(Income) loss from investment in subsidiaries	52,453	63,459	118,351	116,653
Total other expenses	52,453	63,459	118,351	116,653
Net income before income taxes	(52,453)	(63,459)	(118,351)	(116,653)
Provision (benefit) for income taxes:
Net income	(52,453)	(63,459)	(118,351)	(116,653)
Comprehensive income (loss)	$ (52,453)	$ (63,459)	$ (118,351)	$ (116,653)