Guarantor Financial Statements - Condensed Consolidating Statement of Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2015	Mar. 31, 2014
Operating revenue:
Oil production	$ 107,507	$ 138,289
Natural gas production	28,337	56,362
Natural gas liquids production	12,366	27,970
Other operational income	2,160	1,209
Derivative income, net	3,128
Total operating revenue	153,498	223,830
Operating expenses:
Lease operating expenses	27,577	46,903
Transportation, processing and gathering expenses	17,703	14,626
Production taxes	2,515	3,062
Depreciation, depletion, amortization	86,422	82,646
Write-down of oil and gas properties	491,412
Accretion expense	6,409	7,555
Salaries, general and administrative	17,007	16,329
Incentive compensation expense	1,563	3,134
Other operational expense	84	424
Derivative expense, net		599
Total operating expenses	650,692	175,278
Income (loss) from operations	(497,194)	48,552
Other (income) expenses:
Interest expense	10,365	8,357
Interest income	(122)	(143)
Other income	(143)	(707)
Total other (income) expenses	10,100	7,507
Income (loss) before taxes	(507,294)	41,045
Provision (benefit) for income taxes:
Deferred	(179,906)	15,102
Total income taxes	(179,906)	15,102
Net income (loss)	(327,388)	25,943
Comprehensive income (loss)	(339,891)	18,854
Parent [Member]
Operating revenue:
Oil production	4,350	6,636
Natural gas production	16,617	28,839
Natural gas liquids production	9,879	18,254
Other operational income	2,160	1,042
Total operating revenue	33,006	54,771
Operating expenses:
Lease operating expenses	4,976	4,013
Transportation, processing and gathering expenses	16,108	10,317
Production taxes	2,198	1,681
Depreciation, depletion, amortization	42,112	28,055
Write-down of oil and gas properties	491,412
Accretion expense	91	68
Salaries, general and administrative	17,001	16,325
Incentive compensation expense	1,563	3,134
Other operational expense	84	394
Total operating expenses	575,545	63,987
Income (loss) from operations	(542,539)	(9,216)
Other (income) expenses:
Interest expense	10,344	8,353
Interest income	(101)	(79)
Other income	(133)	(181)
Income from investment in subsidiaries	(29,027)	(37,345)
Total other (income) expenses	(18,917)	(29,252)
Income (loss) before taxes	(523,622)	20,036
Provision (benefit) for income taxes:
Deferred	(196,234)	(5,907)
Total income taxes	(196,234)	(5,907)
Net income (loss)	(327,388)	25,943
Comprehensive income (loss)	(339,891)	18,854
Guarantor Subsidiary [Member]
Operating revenue:
Oil production	103,157	131,653
Natural gas production	11,720	27,523
Natural gas liquids production	2,487	9,716
Other operational income		167
Derivative income, net	3,128
Total operating revenue	120,492	169,059
Operating expenses:
Lease operating expenses	22,601	42,890
Transportation, processing and gathering expenses	1,595	4,309
Production taxes	317	1,381
Depreciation, depletion, amortization	44,310	54,591
Accretion expense	6,318	7,487
Salaries, general and administrative	1	2
Other operational expense		30
Derivative expense, net		599
Total operating expenses	75,142	111,289
Income (loss) from operations	45,350	57,770
Other (income) expenses:
Interest expense	21	4
Interest income	(16)	(58)
Other income	(10)	(526)
Total other (income) expenses	(5)	(580)
Income (loss) before taxes	45,355	58,350
Provision (benefit) for income taxes:
Deferred	16,328	21,009
Total income taxes	16,328	21,009
Net income (loss)	29,027	37,341
Comprehensive income (loss)	29,027	37,341
Non-Guarantor Subsidiaries [Member]
Operating expenses:
Salaries, general and administrative	5	2
Total operating expenses	5	2
Income (loss) from operations	(5)	(2)
Other (income) expenses:
Interest income	(5)	(6)
Income from investment in subsidiaries		(4)
Total other (income) expenses	(5)	(10)
Income (loss) before taxes		8
Provision (benefit) for income taxes:
Net income (loss)		8
Comprehensive income (loss)		8
Eliminations [Member]
Other (income) expenses:
Income from investment in subsidiaries	29,027	37,349
Total other (income) expenses	29,027	37,349
Income (loss) before taxes	(29,027)	(37,349)
Provision (benefit) for income taxes:
Net income (loss)	(29,027)	(37,349)
Comprehensive income (loss)	$ (29,027)	$ (37,349)