Condensed Consolidating Statement of Cash Flows (Detail) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Cash flows from operating activities:
Net income (loss)	$ 117,634	$ 149,426	$ 194,332
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	350,574	344,365	280,020
Accretion expense	33,575	33,331	30,764
Deferred income tax provision (benefit)	79,629	69,575	129,520
Settlement of asset retirement obligations	(83,854)	(65,567)	(63,391)
Non-cash stock compensation expense	10,347	8,699	5,905
Excess tax benefits	(156)	(949)	(1,493)
Non-cash derivative expense (income)	2,239	(509)	(2,216)
Loss on early extinguishment of debt	27,279	1,972	607
Non-cash interest expense	16,219	13,085	1,908
Other non-cash income			(1,602)
Change in current income taxes	2,767	10,618	(19,451)
(Increase) decrease in accounts receivable	(4,683)	(55,871)	(19,600)
(Increase) decrease in other current assets	1,752	(2,836)	(66)
Decrease in inventory	583	436	1,619
Increase (decrease) in accounts payable	402	5,101	6,039
Decrease in other current liabilities	42,451	(10,426)	29,583
Other	(2,553)	9,299	(1,628)
Net cash provided by (used in) operating activities	594,205	509,749	570,850
Cash flows from investing activities:
Investment in oil and gas properties	(663,299)	(555,855)	(764,933)
Proceeds from sale of oil and gas properties, net of expenses	48,821	403	87,930
Sale of fixed assets		134
Investment in fixed and other assets	(6,816)	(13,370)	(2,247)
Change in restricted funds	(1,742)
Net cash used in investing activities	(623,036)	(568,688)	(679,250)
Cash flows from financing activities:
Proceeds from bank borrowings		25,000	75,000
Repayment of bank borrowings		(70,000)	(30,000)
Proceeds from issuance of senior convertible notes		300,000
Deferred financing costs of senior convertible notes		(8,855)
Proceeds from sold warrants		40,170
Payments for purchased call options		(70,830)
Proceeds from issuance of senior notes	489,250	300,000
Deferred financing costs	(9,065)	(11,966)	(4,017)
Redemption of senior subordinated notes		(200,681)
Redemption of senior notes	(396,014)
Excess tax benefits	156	949	1,493
Net payments for share-based compensation	(3,733)	(3,773)	(2,581)
Net cash provided by financing activities	80,594	300,014	39,895
Effect of exchange rate changes on cash	(65)
Net change in cash and cash equivalents	51,698	241,075	(68,505)
Cash and cash equivalents, beginning of period	279,526	38,451	106,956
Cash and cash equivalents, end of period	331,224	279,526	38,451
Parent [Member]
Cash flows from operating activities:
Net income (loss)	117,634	149,426	194,332
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	93,579	63,022	17,860
Accretion expense	372	561	15
Deferred income tax provision (benefit)	(41,284)	(56,175)	(1,403)
Non-cash stock compensation expense	10,347	8,699	5,905
Excess tax benefits	(156)	(949)	(1,493)
Loss on early extinguishment of debt	27,279	1,972	607
Non-cash interest expense	16,219	13,085	1,908
Other non-cash income			(1,602)
Non-cash (income) loss from investment in subsidiaries	(214,983)	(223,555)	(230,861)
Change in current income taxes	2,767	10,618	(19,451)
Change in intercompany receivables/payables	186,903	275,819	217,287
(Increase) decrease in accounts receivable	(15,630)	(22,750)	(11,022)
(Increase) decrease in other current assets	1,752	(2,836)	(80)
Decrease in inventory	583	436	1,605
Increase (decrease) in accounts payable	(1,052)	5,348	2,658
Decrease in other current liabilities	40,543	(5,311)	23,440
Other	419	10,960	(1,628)
Net cash provided by (used in) operating activities	225,292	228,370	198,077
Cash flows from investing activities:
Investment in oil and gas properties	(273,474)	(324,542)	(309,026)
Proceeds from sale of oil and gas properties, net of expenses	6,300	403	5,575
Sale of fixed assets		134
Investment in fixed and other assets	(6,816)	(13,370)	(2,247)
Investment in subsidiaries	(14,000)
Net cash used in investing activities	(287,990)	(337,375)	(305,698)
Cash flows from financing activities:
Proceeds from bank borrowings		25,000	75,000
Repayment of bank borrowings		(70,000)	(30,000)
Proceeds from issuance of senior convertible notes		300,000
Deferred financing costs of senior convertible notes		(8,855)
Proceeds from sold warrants		40,170
Payments for purchased call options		(70,830)
Proceeds from issuance of senior notes	489,250	300,000
Deferred financing costs	(9,065)	(11,966)	(4,017)
Redemption of senior subordinated notes		(200,681)
Redemption of senior notes	(396,014)
Excess tax benefits	156	949	1,493
Net payments for share-based compensation	(3,733)	(3,773)	(2,581)
Net cash provided by financing activities	80,594	300,014	39,895
Net change in cash and cash equivalents	17,896	191,009	(67,726)
Cash and cash equivalents, beginning of period	228,398	37,389	105,115
Cash and cash equivalents, end of period	246,294	228,398	37,389
Guarantor Subsidiary [Member]
Cash flows from operating activities:
Net income (loss)	215,009	223,555	232,751
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization	256,995	281,152	261,326
Accretion expense	33,203	32,513	30,385
Deferred income tax provision (benefit)	120,913	125,750	130,923
Settlement of asset retirement obligations	(83,854)	(65,567)	(63,391)
Non-cash derivative expense (income)	2,239	(509)	(2,216)
Non-cash (income) loss from investment in subsidiaries		75	(1,063)
Change in intercompany receivables/payables	(186,947)	(275,125)	(217,724)
(Increase) decrease in accounts receivable	10,947	(33,345)	(7,688)
(Increase) decrease in other current assets			14
Decrease in inventory			14
Increase (decrease) in accounts payable	1,454	(208)	3,341
Decrease in other current liabilities	1,908	(5,115)	6,143
Other	(2,972)	(1,661)
Net cash provided by (used in) operating activities	368,895	281,515	372,815
Cash flows from investing activities:
Investment in oil and gas properties	(378,254)	(231,313)	(455,903)
Proceeds from sale of oil and gas properties, net of expenses	42,521		82,355
Net cash used in investing activities	(335,733)	(231,313)	(373,548)
Cash flows from financing activities:
Net change in cash and cash equivalents	33,162	50,202	(733)
Cash and cash equivalents, beginning of period	51,128	926	1,659
Cash and cash equivalents, end of period	84,290	51,128	926
Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net income (loss)	(52)	(75)	(827)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization		191	834
Accretion expense		257	364
Non-cash (income) loss from investment in subsidiaries	26
Change in intercompany receivables/payables	44	(694)	437
(Increase) decrease in accounts receivable		224	(890)
Increase (decrease) in accounts payable		(39)	40
Net cash provided by (used in) operating activities	18	(136)	(42)
Cash flows from investing activities:
Investment in oil and gas properties	(11,571)		(4)
Change in restricted funds	(1,742)
Investment in subsidiaries	(13,404)
Net cash used in investing activities	(26,717)		(4)
Cash flows from financing activities:
Equity proceeds from parent	27,404
Net cash provided by financing activities	27,404
Effect of exchange rate changes on cash	(65)
Net change in cash and cash equivalents	640	(136)	(46)
Cash and cash equivalents, beginning of period		136	182
Cash and cash equivalents, end of period	640		136
Consolidation, Eliminations [Member]
Cash flows from operating activities:
Net income (loss)	(214,957)	(223,480)	(231,924)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Non-cash (income) loss from investment in subsidiaries	214,957	223,480	231,924
Cash flows from investing activities:
Investment in subsidiaries	27,404
Net cash used in investing activities	27,404
Cash flows from financing activities:
Equity proceeds from parent	(27,404)
Net cash provided by financing activities	$ (27,404)