Guarantor Financial Statements (Details 1) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012	Mar. 31, 2011
Operating revenue:
Oil production	$ 201,758	$ 151,995
Gas production	28,857	41,160
Natural gas liquids production	13,452	5,999
Other operational income	890	885
Total operating revenue	244,957	200,039
Operating expenses:
Lease operating expenses	44,480	38,287
Transportation, processing and gathering expenses	3,657	1,820
Other operational expense	42	662
Production taxes	3,378	2,535
Depreciation, depletion and amortization	84,575	67,669
Accretion expense	8,266	7,717
Salaries, general and administrative expenses	13,705	11,733
Incentive compensation expense	1,442	2,684
Derivative expense, net	485	2,180
Total operating expenses	160,030	135,287
Income from operations	84,927	64,752
Other (income) expenses:
Interest expense	5,731	3,111
Interest income	(31)	(94)
Other income	(420)	(564)
Other expense		124
Total other expenses	5,280	2,577
Net income before income taxes	79,647	62,175
Provision for income taxes:
Current	1,234
Deferred	27,439	22,383
Total income taxes	28,673	22,383
Net income	50,974	39,792
Comprehensive income (loss)	28,909	7,318
Parent [Member]
Operating revenue:
Oil production	6,234	786
Gas production	5,631	1,280
Natural gas liquids production	3,864
Other operational income	694	722
Total operating revenue	16,423	2,788
Operating expenses:
Lease operating expenses	4,904	356
Transportation, processing and gathering expenses	2,488
Other operational expense	42
Production taxes	1,163	147
Depreciation, depletion and amortization	11,477	5,942
Accretion expense	148	4
Salaries, general and administrative expenses	12,654	11,731
Incentive compensation expense	1,442	2,684
Total operating expenses	34,318	20,864
Income from operations	(17,895)	(18,076)
Other (income) expenses:
Interest expense	5,846	3,031
Interest income	(30)	(88)
Other income	(19)
Other expense		123
(Income) loss from investment in subsidiaries	(66,137)	(53,323)
Total other expenses	(60,340)	(50,257)
Net income before income taxes	42,445	32,181
Provision for income taxes:
Current	1,234
Deferred	(9,763)	(7,611)
Total income taxes	(8,529)	(7,611)
Net income	50,974	39,792
Comprehensive income (loss)	28,909	7,318
Guarantor Subsidiary [Member]
Operating revenue:
Oil production	195,524	151,209
Gas production	23,226	39,880
Natural gas liquids production	9,588	5,999
Other operational income	63	(19)
Total operating revenue	228,401	197,069
Operating expenses:
Lease operating expenses	39,387	37,931
Transportation, processing and gathering expenses	1,169	1,820
Other operational expense		662
Production taxes	2,215	2,388
Depreciation, depletion and amortization	73,000	61,510
Accretion expense	8,032	7,622
Salaries, general and administrative expenses	1,051	2
Derivative expense, net	485
Total operating expenses	125,339	114,115
Income from operations	103,062	82,954
Other (income) expenses:
Interest expense	(115)	80
Interest income	(1)	(6)
Other income	(401)	(567)
Other expense		1
(Income) loss from investment in subsidiaries	239	129
Total other expenses	(278)	(363)
Net income before income taxes	103,340	83,317
Provision for income taxes:
Deferred	37,202	29,994
Total income taxes	37,202	29,994
Net income	66,138	53,323
Comprehensive income (loss)	66,138	53,323
Non-Guarantor Subsidiaries [Member]
Operating revenue:
Other operational income	133	182
Total operating revenue	133	182
Operating expenses:
Lease operating expenses	189
Depreciation, depletion and amortization	98	217
Accretion expense	86	91
Total operating expenses	373	308
Income from operations	(240)	(126)
Other (income) expenses:
Other income		3
Total other expenses		3
Net income before income taxes	(240)	(129)
Provision for income taxes:
Net income	(240)	(129)
Comprehensive income (loss)	(240)	(129)
Eliminations [Member]
Other (income) expenses:
(Income) loss from investment in subsidiaries	65,898	53,194
Total other expenses	65,898	53,194
Net income before income taxes	(65,898)	(53,194)
Provision for income taxes:
Net income	(65,898)	(53,194)
Comprehensive income (loss)	$ (65,898)	$ (53,194)