Guarantor Financial Statements - Condensed Consolidating Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Operating revenue:
Oil production	$ 105,013	$ 123,795	$ 324,105	$ 404,477
Natural gas production	17,367	30,154	72,611	133,183
Natural gas liquids production	5,980	21,014	29,379	64,920
Other operational income	1,392	2,468	3,184	5,515
Derivative income, net	2,444	5,782	4,871	2,667
Total operating revenue	132,196	183,213	434,150	610,762
Operating expenses:
Lease operating expenses	24,244	43,561	79,250	139,918
Transportation, processing and gathering expenses	18,208	16,721	55,851	45,445
Production taxes	2,052	3,651	6,394	9,970
Depreciation, depletion and amortization	61,936	80,291	226,309	255,772
Write-down of oil and gas properties	295,679	47,130	1,011,385	47,130
Accretion expense	6,498	6,539	19,315	21,827
Salaries, general and administrative expenses	19,552	16,286	52,977	49,252
Incentive compensation expense	794	3,092	3,621	10,129
Other operational expenses	442	298	1,612	510
Total operating expenses	429,405	217,569	1,456,714	579,953
Income (loss) from operations	(297,209)	(34,356)	(1,022,564)	30,809
Other (income) expenses:
Interest expense	10,872	10,323	31,709	28,593
Interest income	(47)	(169)	(235)	(505)
Other income	(411)	(695)	(1,167)	(2,124)
Other expense	148	95	148	274
Total other expenses	10,562	9,554	30,455	26,238
Provision (benefit) for income taxes:
Income (loss) before income taxes	(307,771)	(43,910)	(1,053,019)	4,571
Total income taxes	(15,806)	(14,495)	(280,760)	3,599
Deferred	(15,806)	(14,495)	(280,760)	3,599
Net income (loss)	(291,965)	(29,415)	(772,259)	972
Comprehensive income (loss)	(297,564)	(65)	(820,517)	14,223
Parent [Member]
Operating revenue:
Oil production	1,633	11,692	12,487	24,182
Natural gas production	7,111	16,001	39,375	65,640
Natural gas liquids production	3,502	15,820	21,458	44,293
Other operational income	1,392	2,417	3,184	5,121
Derivative income, net	0	0		0
Total operating revenue	13,638	45,930	76,504	139,236
Operating expenses:
Lease operating expenses	2,680	5,619	12,767	14,678
Transportation, processing and gathering expenses	13,697	14,379	47,779	35,152
Production taxes	1,777	2,936	5,411	6,520
Depreciation, depletion and amortization	27,518	36,598	113,682	95,038
Write-down of oil and gas properties	295,679	47,130	966,216	47,130
Accretion expense	92	56	274	185
Salaries, general and administrative expenses	19,348	16,273	52,747	49,237
Incentive compensation expense	794	3,092	3,621	10,129
Other operational expenses	142	294	1,312	470
Total operating expenses	361,727	126,377	1,203,809	258,539
Income (loss) from operations	(348,089)	(80,447)	(1,127,305)	(119,303)
Other (income) expenses:
Interest expense	10,871	10,316	31,687	28,549
Interest income	(39)	(76)	(186)	(301)
Other income	(117)	(164)	(437)	(537)
Other expense	148	95	148	274
(Income) loss from investment in subsidiaries	(227,973)	(29,894)	(273,147)	(97,186)
Total other expenses	(217,110)	(19,723)	(241,935)	(69,201)
Provision (benefit) for income taxes:
Income (loss) before income taxes	(130,979)	(60,724)	(885,370)	(50,102)
Total income taxes	160,986	(31,309)	(113,111)	(51,074)
Deferred	160,986	(31,309)	(113,111)	(51,074)
Net income (loss)	(291,965)	(29,415)	(772,259)	972
Comprehensive income (loss)	(297,564)	(65)	(820,517)	14,223
Guarantor Subsidiaries [Member]
Operating revenue:
Oil production	103,380	112,103	311,618	380,295
Natural gas production	10,256	14,153	33,236	67,543
Natural gas liquids production	2,478	5,194	7,921	20,627
Other operational income	0	51		394
Derivative income, net	2,444	5,782	4,871	2,667
Total operating revenue	118,558	137,283	357,646	471,526
Operating expenses:
Lease operating expenses	21,562	37,942	66,481	125,240
Transportation, processing and gathering expenses	4,511	2,342	8,072	10,293
Production taxes	275	715	983	3,450
Depreciation, depletion and amortization	34,418	43,693	112,627	160,734
Write-down of oil and gas properties		0		0
Accretion expense	6,406	6,483	19,041	21,642
Salaries, general and administrative expenses	200	1	201	3
Other operational expenses	300	4	300	40
Total operating expenses	67,672	91,180	207,705	321,402
Income (loss) from operations	50,886	46,103	149,941	150,124
Other (income) expenses:
Interest expense	1	7	22	44
Interest income	(7)	(82)	(42)	(181)
Other income	(294)	(531)	(727)	(1,587)
Other expense	0
Total other expenses	(300)	(606)	(747)	(1,724)
Provision (benefit) for income taxes:
Income (loss) before income taxes	51,186	46,709	150,688	151,848
Total income taxes	(193,059)	16,814	(167,649)	54,673
Deferred	(193,059)	16,814	(167,649)	54,673
Net income (loss)	244,245	29,895	318,337	97,175
Comprehensive income (loss)	244,245	29,895	318,337	97,175
Non-Guarantor Subsidiaries [Member]
Operating expenses:
Lease operating expenses	2		2
Write-down of oil and gas properties	0		45,169
Salaries, general and administrative expenses	4	12	29	12
Total operating expenses	6	12	45,200	12
Income (loss) from operations	(6)	(12)	(45,200)	(12)
Other (income) expenses:
Interest income	(1)	(11)	(7)	(23)
Other income	0		(3)
Other expense	0
(Income) loss from investment in subsidiaries	16,272	2	45,190	(10)
Total other expenses	16,271	(9)	45,180	(33)
Provision (benefit) for income taxes:
Income (loss) before income taxes	(16,277)	(3)	(90,380)	21
Total income taxes	16,267		0
Deferred	16,267		0
Net income (loss)	(32,544)	(3)	(90,380)	21
Comprehensive income (loss)	(32,544)	(3)	(90,380)	21
Eliminations [Member]
Other (income) expenses:
(Income) loss from investment in subsidiaries	211,701	29,892	227,957	97,196
Total other expenses	211,701	29,892	227,957	97,196
Provision (benefit) for income taxes:
Income (loss) before income taxes	(211,701)	(29,892)	(227,957)	(97,196)
Net income (loss)	(211,701)	(29,892)	(227,957)	(97,196)
Comprehensive income (loss)	$ (211,701)	$ (29,892)	$ (227,957)	$ (97,196)