Guarantor Financial Statements - Condensed Consolidating Statement of Operations (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Operating revenue:
Oil production	$ 111,585	$ 142,393	$ 219,092	$ 280,682
Natural gas production	26,907	46,667	55,244	103,029
Natural gas liquids production	11,033	15,936	23,399	43,906
Other operational income		2,050	1,792	3,047
Derivative income, net			2,427
Total operating revenue	149,525	207,046	301,954	430,664
Operating expenses:
Lease operating expenses	27,429	49,454	55,006	96,357
Transportation, processing and gathering expenses	19,940	14,098	37,643	28,724
Production taxes	1,827	3,257	4,342	6,319
Depreciation, depletion, amortization	77,951	92,835	164,373	175,481
Write-down of oil and gas properties	224,294		715,706
Accretion expense	6,408	7,733	12,817	15,288
Salaries, general and administrative	16,418	16,637	33,425	32,966
Incentive compensation expense	1,264	3,903	2,827	7,037
Other operational expense	1,454		1,170	212
Derivative expense, net	701	2,516		3,115
Total operating expenses	377,686	190,433	1,027,309	365,499
Income (loss) from operations	(228,161)	16,613	(725,355)	65,165
Other (income) expenses:
Interest expense	10,472	9,913	20,837	18,270
Interest income	(66)	(193)	(188)	(336)
Other income	(613)	(722)	(756)	(1,429)
Other expense		179		179
Total other (income) expenses	9,793	9,177	19,893	16,684
Income (loss) before taxes	(237,954)	7,436	(745,248)	48,481
Provision (benefit) for income taxes:
Deferred	(85,048)	2,992	(264,954)	18,094
Total income taxes	(85,048)	2,992	(264,954)	18,094
Net income (loss)	(152,906)	4,444	(480,294)	30,387
Comprehensive income (loss)	(183,062)	(4,566)	(522,953)	14,288
Parent [Member]
Operating revenue:
Oil production	6,504	5,854	10,854	12,490
Natural gas production	15,647	20,800	32,264	49,639
Natural gas liquids production	8,077	10,219	17,956	28,473
Other operational income		1,880	1,792	2,704
Total operating revenue	30,228	38,753	62,866	93,306
Operating expenses:
Lease operating expenses	5,111	5,046	10,087	9,059
Transportation, processing and gathering expenses	17,974	10,456	34,082	20,773
Production taxes	1,436	1,903	3,634	3,584
Depreciation, depletion, amortization	44,052	30,385	86,164	58,440
Write-down of oil and gas properties	179,125		670,537
Accretion expense	91	61	182	129
Salaries, general and administrative	16,398	16,639	33,399	32,964
Incentive compensation expense	1,264	3,903	2,827	7,037
Other operational expense	1,454		1,170	176
Total operating expenses	266,905	68,393	842,082	132,162
Income (loss) from operations	(236,677)	(29,640)	(779,216)	(38,856)
Other (income) expenses:
Interest expense	10,472	9,880	20,816	18,233
Interest income	(46)	(146)	(147)	(225)
Other income	(187)	(192)	(320)	(373)
Other expense		179		179
(Income) loss from investment in subsidiaries	(16,147)	(29,947)	(45,174)	(67,292)
Total other (income) expenses	(5,908)	(20,226)	(24,825)	(49,478)
Income (loss) before taxes	(230,769)	(9,414)	(754,391)	10,622
Provision (benefit) for income taxes:
Deferred	(77,863)	(13,858)	(274,097)	(19,765)
Total income taxes	(77,863)	(13,858)	(274,097)	(19,765)
Net income (loss)	(152,906)	4,444	(480,294)	30,387
Comprehensive income (loss)	(183,062)	(4,566)	(522,953)	14,288
Guarantor Subsidiaries [Member]
Operating revenue:
Oil production	105,081	136,539	208,238	268,192
Natural gas production	11,260	25,867	22,980	53,390
Natural gas liquids production	2,956	5,717	5,443	15,433
Other operational income		170		343
Derivative income, net			2,427
Total operating revenue	119,297	168,293	239,088	337,358
Operating expenses:
Lease operating expenses	22,318	44,408	44,919	87,298
Transportation, processing and gathering expenses	1,966	3,642	3,561	7,951
Production taxes	391	1,354	708	2,735
Depreciation, depletion, amortization	33,899	62,450	78,209	117,041
Accretion expense	6,317	7,672	12,635	15,159
Salaries, general and administrative			1	2
Other operational expense				36
Derivative expense, net	701	2,516		3,115
Total operating expenses	65,592	122,042	140,033	233,337
Income (loss) from operations	53,705	46,251	99,055	104,021
Other (income) expenses:
Interest expense		33	21	37
Interest income	(19)	(41)	(35)	(99)
Other income	(423)	(530)	(433)	(1,056)
Total other (income) expenses	(442)	(538)	(447)	(1,118)
Income (loss) before taxes	54,147	46,789	99,502	105,139
Provision (benefit) for income taxes:
Deferred	9,082	16,850	25,410	37,859
Total income taxes	9,082	16,850	25,410	37,859
Net income (loss)	45,065	29,939	74,092	67,280
Comprehensive income (loss)	45,065	29,939	74,092	67,280
Non-Guarantor Subsidiaries [Member]
Operating expenses:
Write-down of oil and gas properties	45,169		45,169
Salaries, general and administrative	20	(2)	25
Total operating expenses	45,189	(2)	45,194
Income (loss) from operations	(45,189)	2	(45,194)
Other (income) expenses:
Interest income	(1)	(6)	(6)	(12)
Other income	(3)		(3)
(Income) loss from investment in subsidiaries	28,918	(8)	28,918	(12)
Total other (income) expenses	28,914	(14)	28,909	(24)
Income (loss) before taxes	(74,103)	16	(74,103)	24
Provision (benefit) for income taxes:
Deferred	(16,267)		(16,267)
Total income taxes	(16,267)		(16,267)
Net income (loss)	(57,836)	16	(57,836)	24
Comprehensive income (loss)	(57,836)	16	(57,836)	24
Eliminations [Member]
Other (income) expenses:
(Income) loss from investment in subsidiaries	(12,771)	29,955	16,256	67,304
Total other (income) expenses	(12,771)	29,955	16,256	67,304
Income (loss) before taxes	12,771	(29,955)	(16,256)	(67,304)
Provision (benefit) for income taxes:
Net income (loss)	12,771	(29,955)	(16,256)	(67,304)
Comprehensive income (loss)	$ 12,771	$ (29,955)	$ (16,256)	$ (67,304)