Guarantor Financial Statements - Condensed Consolidating Statement of Operations (Detail) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013
Operating revenue:
Oil production	$ 123,795	$ 186,608	$ 404,477	$ 558,031
Gas production	30,154	52,728	133,183	137,382
Natural gas liquids production	21,014	16,476	64,920	36,854
Other operational income	2,468	873	5,515	2,659
Derivative income, net	5,782		2,667
Total operating revenue	183,213	256,685	610,762	734,926
Operating expenses:
Lease operating expenses	43,561	53,986	139,918	157,547
Transportation, processing and gathering expenses	16,721	13,081	45,445	27,374
Production taxes	3,651	5,224	9,970	11,404
Depreciation, depletion, amortization	80,291	92,853	255,772	255,497
Write-down of oil and gas properties	47,130		47,130
Accretion expense	6,539	8,431	21,827	25,012
Salaries, general and administrative	16,286	14,201	49,252	43,351
Incentive compensation expense	3,092	4,566	10,129	8,047
Other operational expenses	298	237	510	382
Derivative expense, net		1,684		1,537
Total operating expenses	217,569	194,263	579,953	530,151
Income (loss) from operations	(34,356)	62,422	30,809	204,775
Other (income) expenses:
Interest expense	10,323	7,922	28,593	26,452
Interest income	(169)	(1,311)	(505)	(1,543)
Other income	(695)	(782)	(2,124)	(2,190)
Other expense	95		274
Total other (income) expenses	9,554	5,829	26,238	22,719
Income (loss) before taxes	(43,910)	56,593	4,571	182,056
Provision (benefit) for income taxes:
Current		(88)		(10,827)
Deferred	(14,495)	20,579	3,599	77,001
Total income taxes	(14,495)	20,491	3,599	66,174
Net income (loss)	(29,415)	36,102	972	115,882
Comprehensive income (loss)	(65)	17,985	14,223	93,462
Eliminations [Member]
Other (income) expenses:
(Income) loss from investment in subsidiaries	29,892	56,173	97,196	168,855
Total other (income) expenses	29,892	56,173	97,196	168,855
Income (loss) before taxes	(29,892)	(56,173)	(97,196)	(168,855)
Provision (benefit) for income taxes:
Net income (loss)	(29,892)	(56,173)	(97,196)	(168,855)
Comprehensive income (loss)	(29,892)	(56,173)	(97,196)	(168,855)
Parent [Member]
Operating revenue:
Oil production	11,692	6,904	24,182	20,625
Gas production	16,001	19,971	65,640	47,240
Natural gas liquids production	15,820	9,224	44,293	17,901
Other operational income	2,417	711	5,121	2,150
Total operating revenue	45,930	36,810	139,236	87,916
Operating expenses:
Lease operating expenses	5,619	3,895	14,678	9,611
Transportation, processing and gathering expenses	14,379	10,072	35,152	17,853
Production taxes	2,936	1,773	6,520	3,960
Depreciation, depletion, amortization	36,598	26,728	95,038	62,007
Write-down of oil and gas properties	47,130		47,130
Accretion expense	56	93	185	279
Salaries, general and administrative	16,273	14,202	49,237	43,300
Incentive compensation expense	3,092	4,566	10,129	8,047
Other operational expenses	294	194	470	295
Total operating expenses	126,377	61,523	258,539	145,352
Income (loss) from operations	(80,447)	(24,713)	(119,303)	(57,436)
Other (income) expenses:
Interest expense	10,316	7,922	28,549	26,431
Interest income	(76)	(1,234)	(301)	(1,384)
Other income	(164)	(230)	(537)	(671)
Other expense	95		274
(Income) loss from investment in subsidiaries	(29,894)	(56,166)	(97,186)	(168,887)
Total other (income) expenses	(19,723)	(49,708)	(69,201)	(144,511)
Income (loss) before taxes	(60,724)	24,995	(50,102)	87,075
Provision (benefit) for income taxes:
Current		(88)		(10,827)
Deferred	(31,309)	(11,019)	(51,074)	(17,980)
Total income taxes	(31,309)	(11,107)	(51,074)	(28,807)
Net income (loss)	(29,415)	36,102	972	115,882
Comprehensive income (loss)	(65)	17,985	14,223	93,462
Guarantor Subsidiary [Member]
Operating revenue:
Oil production	112,103	179,704	380,295	537,406
Gas production	14,153	32,757	67,543	90,142
Natural gas liquids production	5,194	7,252	20,627	18,953
Other operational income	51	162	394	509
Derivative income, net	5,782		2,667
Total operating revenue	137,283	219,875	471,526	647,010
Operating expenses:
Lease operating expenses	37,942	50,091	125,240	147,936
Transportation, processing and gathering expenses	2,342	3,009	10,293	9,521
Production taxes	715	3,451	3,450	7,444
Depreciation, depletion, amortization	43,693	66,125	160,734	193,490
Accretion expense	6,483	8,338	21,642	24,733
Salaries, general and administrative	1		3	4
Other operational expenses	4	43	40	87
Derivative expense, net		1,684		1,537
Total operating expenses	91,180	132,741	321,402	384,752
Income (loss) from operations	46,103	87,134	150,124	262,258
Other (income) expenses:
Interest expense	7		44	21
Interest income	(82)	(69)	(181)	(144)
Other income	(531)	(552)	(1,587)	(1,519)
Total other (income) expenses	(606)	(621)	(1,724)	(1,642)
Income (loss) before taxes	46,709	87,755	151,848	263,900
Provision (benefit) for income taxes:
Deferred	16,814	31,598	54,673	94,981
Total income taxes	16,814	31,598	54,673	94,981
Net income (loss)	29,895	56,157	97,175	168,919
Comprehensive income (loss)	(29,895)	56,157	97,175	168,919
Non-Guarantor Subsidiaries [Member]
Operating expenses:
Salaries, general and administrative	12	(1)	12	47
Total operating expenses	12	(1)	12	47
Income (loss) from operations	(12)	1	(12)	(47)
Other (income) expenses:
Interest income	(11)	(8)	(23)	(15)
(Income) loss from investment in subsidiaries	2	(7)	(10)	32
Total other (income) expenses	(9)	(15)	(33)	17
Income (loss) before taxes	(3)	16	21	(64)
Provision (benefit) for income taxes:
Net income (loss)	(3)	16	21	(64)
Comprehensive income (loss)	$ (3)	$ 16	$ 21	$ (64)