Guarantor Financial Statements - Condensed Consolidating Statement of Cash Flows (Detail) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2014	Sep. 30, 2014	Jun. 30, 2014	Mar. 31, 2014	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Cash flows from operating activities:
Net income (loss)	$ (318,656)	$ (291,965)	$ (152,906)	$ (327,388)	$ (190,515)	$ (29,415)	$ 4,444	$ 25,943	$ (1,090,915)	$ (189,543)	$ 117,634
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization									281,688	340,006	350,574
Write-down of oil and gas properties	351,062	$ 295,679	$ 224,294	491,412	304,062	$ 47,130	$ 0	0	1,362,447	351,192	0
Accretion expense									25,988	28,411	33,575
Deferred income tax (benefit) provision									(272,311)	(102,177)	79,629
Settlement of asset retirement obligations									(72,382)	(56,409)	(83,854)
Non-cash stock compensation expense									12,324	11,325	10,347
Excess tax benefits									(1,586)	0	(156)
Non-cash derivative income									16,440	(18,028)	2,239
Loss on early extinguishment of debt									0	0	27,279
Non-cash interest expense									17,788	16,661	16,219
Change in current income taxes									(37,377)	158	2,767
Non-cash income from investment in subsidiaries									0	0	0
Change in intercompany receivables/payables									0	0	0
(Increase) decrease in accounts receivable									43,724	51,611	(4,683)
(Increase) decrease in other current assets									1,767	(6,244)	1,752
(Increase) decrease in inventory									1,304	0	583
Decrease in accounts payable									(14,582)	(3,419)	402
Increase (decrease) in other current liabilities									(25,936)	(19,152)	42,451
Other									(907)	(3,251)	(2,553)
Net cash provided by operating activities									247,474	401,141	594,205
Cash flows from investing activities:
Investment in oil and gas properties									(522,047)	(927,247)	(663,299)
Proceeds from sale of oil and gas properties, net of expenses									22,839	242,914	48,821
Investment in fixed and other assets									(1,549)	(10,182)	(6,816)
Change in restricted funds									179,467	(178,072)	(1,742)
Investment in subsidiaries									0	0	0
Net cash used in investing activities									(321,290)	(872,587)	(623,036)
Cash flows from financing activities:
Proceeds from bank borrowings									5,000	0	0
Proceeds from issuance of common stock									0	225,999	0
Repayments of bank borrowings									(5,000)	0	0
Proceeds from issuance of senior notes									0	0	489,250
Deferred financing costs									(68)	(3,371)	(9,065)
Proceeds from building loan									11,770	0	0
Redemption of senior notes									0	0	(396,014)
Excess tax benefits									1,586	0	156
Equity proceeds from parent									0	0	0
Net payments for share-based compensation									(3,127)	(7,182)	(3,733)
Net cash provided by financing activities									10,161	215,446	80,594
Effect of exchange rate changes on cash									(74)	(736)	(65)
Net change in cash and cash equivalents									(63,729)	(256,736)	51,698
Cash and cash equivalents, beginning of year				74,488				331,224	74,488	331,224	279,526
Cash and cash equivalents, end of year	10,759				74,488				10,759	74,488	331,224
Parent [Member]
Cash flows from operating activities:
Net income (loss)									(1,090,915)	(189,543)	117,634
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization									123,724	138,313	93,579
Write-down of oil and gas properties									785,463	351,192
Accretion expense									365	230	372
Deferred income tax (benefit) provision									(114,418)	(177,197)	(41,284)
Settlement of asset retirement obligations									(15)	(201)	0
Non-cash stock compensation expense									12,324	11,325	10,347
Excess tax benefits									(1,586)		(156)
Non-cash derivative income									0	0	0
Loss on early extinguishment of debt											27,279
Non-cash interest expense									17,788	16,661	16,219
Change in current income taxes									(37,377)	158	2,767
Non-cash income from investment in subsidiaries									231,783	(133,336)	(214,983)
Change in intercompany receivables/payables									9,744	114,056	186,903
(Increase) decrease in accounts receivable									34,609	1,131	(15,630)
(Increase) decrease in other current assets									1,799	(6,238)	1,752
(Increase) decrease in inventory									(1,394)	2,415	583
Decrease in accounts payable									(7,471)	(662)	(1,052)
Increase (decrease) in other current liabilities									(25,989)	(16,946)	40,543
Other									256	(1,755)	419
Net cash provided by operating activities									(61,310)	109,603	225,292
Cash flows from investing activities:
Investment in oil and gas properties									(188,154)	(338,731)	(273,474)
Proceeds from sale of oil and gas properties, net of expenses									0	28,103	6,300
Investment in fixed and other assets									(1,549)	(10,182)	(6,816)
Change in restricted funds									177,647	(177,647)	0
Investment in subsidiaries									0	0	(14,000)
Net cash used in investing activities									(12,056)	(498,457)	(287,990)
Cash flows from financing activities:
Proceeds from bank borrowings									5,000
Proceeds from issuance of common stock										225,999
Repayments of bank borrowings									(5,000)
Proceeds from issuance of senior notes											489,250
Deferred financing costs									(68)	(3,371)	(9,065)
Proceeds from building loan									11,770
Redemption of senior notes											(396,014)
Excess tax benefits									1,586		156
Equity proceeds from parent									0	0	0
Net payments for share-based compensation									(3,127)	(7,182)	(3,733)
Net cash provided by financing activities									10,161	215,446	80,594
Effect of exchange rate changes on cash									0	0	0
Net change in cash and cash equivalents									(63,205)	(173,408)	17,896
Cash and cash equivalents, beginning of year				72,886				246,294	72,886	246,294	228,398
Cash and cash equivalents, end of year	9,681				72,886				9,681	72,886	246,294
Guarantor Subsidiary [Member]
Cash flows from operating activities:
Net income (loss)									(184,124)	133,304	215,009
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization									157,964	201,693	256,995
Write-down of oil and gas properties									529,354	0
Accretion expense									25,623	28,181	33,203
Deferred income tax (benefit) provision									(157,893)	75,020	120,913
Settlement of asset retirement obligations									(72,367)	(56,208)	(83,854)
Non-cash stock compensation expense									0	0	0
Excess tax benefits									0		0
Non-cash derivative income									16,440	(18,028)	2,239
Loss on early extinguishment of debt											0
Non-cash interest expense									0	0	0
Change in current income taxes									0	0	0
Non-cash income from investment in subsidiaries									0	0	0
Change in intercompany receivables/payables									(19,486)	(145,250)	(186,947)
(Increase) decrease in accounts receivable									9,084	50,514	10,947
(Increase) decrease in other current assets									0	0	0
(Increase) decrease in inventory									2,698	(2,415)	0
Decrease in accounts payable									(7,111)	(2,757)	1,454
Increase (decrease) in other current liabilities									53	(2,206)	1,908
Other									(1,163)	(1,496)	(2,972)
Net cash provided by operating activities									299,072	260,352	368,895
Cash flows from investing activities:
Investment in oil and gas properties									(323,359)	(558,003)	(378,254)
Proceeds from sale of oil and gas properties, net of expenses									22,839	214,811	42,521
Investment in fixed and other assets									0	0	0
Change in restricted funds									0	0	0
Investment in subsidiaries									0	0	0
Net cash used in investing activities									(300,520)	(343,192)	(335,733)
Cash flows from financing activities:
Proceeds from bank borrowings									0
Proceeds from issuance of common stock										0
Repayments of bank borrowings									0
Proceeds from issuance of senior notes											0
Deferred financing costs									0	0	0
Proceeds from building loan									0
Redemption of senior notes											0
Excess tax benefits									0		0
Equity proceeds from parent									0	0	0
Net payments for share-based compensation									0	0	0
Net cash provided by financing activities									0	0	0
Effect of exchange rate changes on cash									0	0	0
Net change in cash and cash equivalents									(1,448)	(82,840)	33,162
Cash and cash equivalents, beginning of year				1,450				84,290	1,450	84,290	51,128
Cash and cash equivalents, end of year	2				1,450				2	1,450	84,290
Non-Guarantor Subsidiaries [Member]
Cash flows from operating activities:
Net income (loss)									(95,318)	64	(52)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization									0	0	0
Write-down of oil and gas properties									47,630	0
Accretion expense									0	0	0
Deferred income tax (benefit) provision									0	0	0
Settlement of asset retirement obligations									0	0	0
Non-cash stock compensation expense									0	0	0
Excess tax benefits									0		0
Non-cash derivative income									0	0	0
Loss on early extinguishment of debt											0
Non-cash interest expense									0	0	0
Change in current income taxes									0	0	0
Non-cash income from investment in subsidiaries									47,659	(32)	26
Change in intercompany receivables/payables									9,742	31,194	44
(Increase) decrease in accounts receivable									31	(34)	0
(Increase) decrease in other current assets									(32)	(6)	0
(Increase) decrease in inventory									0	0	0
Decrease in accounts payable									0	0	0
Increase (decrease) in other current liabilities									0	0	0
Other									0	0	0
Net cash provided by operating activities									9,712	31,186	18
Cash flows from investing activities:
Investment in oil and gas properties									(10,534)	(30,513)	(11,571)
Proceeds from sale of oil and gas properties, net of expenses									0	0	0
Investment in fixed and other assets									0	0	0
Change in restricted funds									1,820	(425)	(1,742)
Investment in subsidiaries									(9,714)	(31,696)	(13,404)
Net cash used in investing activities									(18,428)	(62,634)	(26,717)
Cash flows from financing activities:
Proceeds from bank borrowings									0
Proceeds from issuance of common stock										0
Repayments of bank borrowings									0
Proceeds from issuance of senior notes											0
Deferred financing costs									0	0	0
Proceeds from building loan									0
Redemption of senior notes											0
Excess tax benefits									0		0
Equity proceeds from parent									9,714	31,696	27,404
Net payments for share-based compensation									0	0	0
Net cash provided by financing activities									9,714	31,696	27,404
Effect of exchange rate changes on cash									(74)	(736)	(65)
Net change in cash and cash equivalents									924	(488)	640
Cash and cash equivalents, beginning of year				152				640	152	640	0
Cash and cash equivalents, end of year	1,076				152				1,076	152	640
Eliminations [Member]
Cash flows from operating activities:
Net income (loss)									279,442	(133,368)	(214,957)
Adjustments to reconcile net income (loss) to net cash provided by operating activities:
Depreciation, depletion and amortization									0	0	0
Write-down of oil and gas properties									0	0
Accretion expense									0	0	0
Deferred income tax (benefit) provision									0	0	0
Settlement of asset retirement obligations									0	0	0
Non-cash stock compensation expense									0	0	0
Excess tax benefits									0		0
Non-cash derivative income									0	0	0
Loss on early extinguishment of debt											0
Non-cash interest expense									0	0	0
Change in current income taxes									0	0	0
Non-cash income from investment in subsidiaries									(279,442)	133,368	214,957
Change in intercompany receivables/payables									0	0	0
(Increase) decrease in accounts receivable									0	0	0
(Increase) decrease in other current assets									0	0	0
(Increase) decrease in inventory									0	0	0
Decrease in accounts payable									0	0	0
Increase (decrease) in other current liabilities									0	0	0
Other									0	0	0
Net cash provided by operating activities									0	0	0
Cash flows from investing activities:
Investment in oil and gas properties									0	0	0
Proceeds from sale of oil and gas properties, net of expenses									0	0	0
Investment in fixed and other assets									0	0	0
Change in restricted funds									0	0	0
Investment in subsidiaries									9,714	31,696	27,404
Net cash used in investing activities									9,714	31,696	27,404
Cash flows from financing activities:
Proceeds from bank borrowings									0
Proceeds from issuance of common stock										0
Repayments of bank borrowings									0
Proceeds from issuance of senior notes											0
Deferred financing costs									0	0	0
Proceeds from building loan									0
Redemption of senior notes											0
Excess tax benefits									0		0
Equity proceeds from parent									(9,714)	(31,696)	(27,404)
Net payments for share-based compensation									0	0	0
Net cash provided by financing activities									(9,714)	(31,696)	(27,404)
Effect of exchange rate changes on cash									0	0	0
Net change in cash and cash equivalents									0	0	0
Cash and cash equivalents, beginning of year				$ 0				$ 0	0	0	0
Cash and cash equivalents, end of year	$ 0				$ 0				$ 0	$ 0	$ 0