Condensed Consolidating Financial Information (Schedule Of Condensed Consolidating Statement Of Operations) (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Revenues
Oil and gas revenues	$ 178,748	$ 87,596	$ 461,857	$ 213,546
Well services revenues	5,963		10,484
Total revenues	184,711	87,596	472,341	213,546
Expenses
Lease operating expenses	16,134	9,597	37,979	21,178
Well services operating expenses	5,420		7,104
Marketing, transportation and gathering expenses	2,744	238	7,283	797
Production taxes	16,433	8,873	43,419	22,041
Depreciation, depletion and amortization	57,684	20,859	140,783	47,771
Exploration expenses	336	54	3,171	345
Impairment of oil and gas properties	36	396	2,607	3,313
General and administrative expenses	13,886	7,306	39,622	19,870
Total expenses	112,673	47,323	281,968	115,315
Operating income (loss)	72,038	40,273	190,373	98,231
Other income (expense)
Net gain (loss) on derivative instruments	(22,441)	71,224	33,568	67,105
Interest expense	(20,979)	(6,786)	(48,952)	(18,745)
Other income	1,147	524	2,521	1,215
Total other income (expense)	(42,273)	64,962	(12,863)	49,575
Income before income taxes	29,765	105,235	177,510	147,806
Income tax benefit (expense)	(11,451)	(38,946)	(66,712)	(55,015)
Net income	18,314	66,289	110,798	92,791
Parent/Issuer [Member]
Expenses
General and administrative expenses	2,988	1,282	8,078	3,863
Total expenses	2,988	1,282	8,078	3,863
Operating income (loss)	(2,988)	(1,282)	(8,078)	(3,863)
Other income (expense)
Equity in earnings in subsidiaries	32,735	71,445	145,021	105,832
Interest expense	(20,307)	(6,495)	(47,136)	(17,909)
Other income	238	282	533	946
Total other income (expense)	12,666	65,232	98,418	88,869
Income before income taxes	9,678	63,950	90,340	85,006
Income tax benefit (expense)	8,636	2,339	20,458	7,785
Net income	18,314	66,289	110,798	92,791
Combined Guarantor Subsidiaries [Member]
Revenues
Oil and gas revenues	178,748	87,596	461,857	213,546
Well services revenues	5,963		10,484
Total revenues	184,711		472,341
Expenses
Lease operating expenses	16,134	9,597	37,979	21,178
Well services operating expenses	5,420		7,104
Marketing, transportation and gathering expenses	2,744	238	7,283	797
Production taxes	16,433	8,873	43,419	22,041
Depreciation, depletion and amortization	57,684	20,859	140,783	47,771
Exploration expenses	336	54	3,171	345
Impairment of oil and gas properties	36	396	2,607	3,313
General and administrative expenses	10,898	6,024	31,544	16,007
Total expenses	109,685	46,041	273,890	111,452
Operating income (loss)	75,026	41,555	198,451	102,094
Other income (expense)
Net gain (loss) on derivative instruments	(22,441)	71,224	33,568	67,105
Interest expense	(672)	(291)	(1,816)	(836)
Other income	909	242	1,988	269
Total other income (expense)	(22,204)	71,175	33,740	66,538
Income before income taxes	52,822	112,730	232,191	168,632
Income tax benefit (expense)	(20,087)	(41,285)	(87,170)	(62,800)
Net income	32,735	71,445	145,021	105,832
Intercompany Eliminations [Member]
Other income (expense)
Equity in earnings in subsidiaries	(32,735)	(71,445)	(145,021)	(105,832)
Total other income (expense)	(32,735)	(71,445)	(145,021)	(105,832)
Income before income taxes	(32,735)	(71,445)	(145,021)	(105,832)
Net income	$ (32,735)	$ (71,445)	$ (145,021)	$ (105,832)