Guarantor Financial Statements - Condensed Consolidating Statement of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015
Cash flows from operating activities:
Net loss	$ (89,635)	$ (291,965)	$ (474,180)	$ (772,259)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion and amortization	58,918	61,936	166,707	226,309
Write-down of oil and gas properties	36,484	295,679	284,337	1,011,385
Accretion expense	10,082	6,498	30,147	19,315
Deferred income tax provision (benefit)	1,888	(15,806)	10,947	(280,760)
Settlement of asset retirement obligations			(15,106)	(59,826)
Non-cash stock compensation expense			6,407	9,163
Non-cash derivative expense			1,261	10,854
Non-cash interest expense			14,278	13,210
Other non-cash expense			6,081	0
Change in current income taxes			21,584	7,211
Non-cash loss from investment in subsidiaries			0	0
Change in intercompany receivables/payables			0	0
(Increase) decrease in accounts receivable			3,968	33,895
Increase in other current assets			(4,426)	(1,090)
(Increase) decrease in inventory				0
Increase (decrease) in accounts payable			3,217	(11,592)
Decrease in other current liabilities			(14,222)	(6,753)
Other			(8,107)	(82)
Net cash provided by operating activities			32,893	198,980
Cash flows from investing activities:
Investment in oil and gas properties			(200,622)	(385,528)
Proceeds from sale of oil and gas properties, net of expenses			0	11,643
Investment in fixed and other assets			(1,231)	(1,455)
Change in restricted funds			1,046	179,475
Investment in subsidiaries			0	0
Net cash used in investing activities			(200,807)	(195,865)
Cash flows from financing activities:
Proceeds from bank borrowings			477,000	5,000
Repayments of bank borrowings			(135,500)	(5,000)
Repayments of building loan			(285)	0
Deferred financing costs			(900)	0
Equity proceeds from parent			0	0
Net payments for share-based compensation			(752)	(3,127)
Net cash provided by (used in) financing activities			339,563	(3,127)
Effect of exchange rate changes on cash			(9)	(2)
Net change in cash and cash equivalents			171,640	(14)
Cash and cash equivalents, beginning of period			10,759	74,488
Cash and cash equivalents, end of period	182,399	74,474	182,399	74,474
Eliminations
Cash flows from operating activities:
Net loss	19,301	(211,701)	256,474	(227,957)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion and amortization	0	0	0	0
Write-down of oil and gas properties	0	0	0	0
Accretion expense	0	0	0	0
Deferred income tax provision (benefit)	0	0	0	0
Settlement of asset retirement obligations			0	0
Non-cash stock compensation expense			0	0
Non-cash derivative expense			0	0
Non-cash interest expense			0	0
Other non-cash expense			0
Change in current income taxes			0	0
Non-cash loss from investment in subsidiaries			(256,474)	227,957
Change in intercompany receivables/payables			0	0
(Increase) decrease in accounts receivable			0	0
Increase in other current assets			0	0
(Increase) decrease in inventory				0
Increase (decrease) in accounts payable			0	0
Decrease in other current liabilities			0	0
Other			0	0
Net cash provided by operating activities			0	0
Cash flows from investing activities:
Investment in oil and gas properties			0	0
Proceeds from sale of oil and gas properties, net of expenses				0
Investment in fixed and other assets			0	0
Change in restricted funds			0	0
Investment in subsidiaries			(716)	9,708
Net cash used in investing activities			(716)	9,708
Cash flows from financing activities:
Proceeds from bank borrowings			0	0
Repayments of bank borrowings			0	0
Repayments of building loan			0
Deferred financing costs			0
Equity proceeds from parent			716	(9,708)
Net payments for share-based compensation			0	0
Net cash provided by (used in) financing activities			716	(9,708)
Effect of exchange rate changes on cash			0	0
Net change in cash and cash equivalents			0	0
Cash and cash equivalents, beginning of period			0	0
Cash and cash equivalents, end of period	0	0	0	0
Parent
Cash flows from operating activities:
Net loss	(89,635)	(291,965)	(474,180)	(772,259)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion and amortization	26,388	27,518	45,452	113,682
Write-down of oil and gas properties	1	295,679	15,859	966,216
Accretion expense	58	92	174	274
Deferred income tax provision (benefit)	0	160,986	0	(113,111)
Settlement of asset retirement obligations			(78)	(15)
Non-cash stock compensation expense			6,407	9,163
Non-cash derivative expense			0	0
Non-cash interest expense			14,278	13,210
Other non-cash expense			0
Change in current income taxes			21,584	7,211
Non-cash loss from investment in subsidiaries			250,029	(273,147)
Change in intercompany receivables/payables			(1,658)	31,320
(Increase) decrease in accounts receivable			7,966	29,561
Increase in other current assets			(4,459)	(1,050)
(Increase) decrease in inventory				(2,415)
Increase (decrease) in accounts payable			7,385	(7,562)
Decrease in other current liabilities			(13,924)	(6,855)
Other			(7,389)	645
Net cash provided by operating activities			(132,554)	(5,132)
Cash flows from investing activities:
Investment in oil and gas properties			(63,075)	(177,497)
Proceeds from sale of oil and gas properties, net of expenses				0
Investment in fixed and other assets			(1,231)	(1,455)
Change in restricted funds			0	177,647
Investment in subsidiaries			0	0
Net cash used in investing activities			(64,306)	(1,305)
Cash flows from financing activities:
Proceeds from bank borrowings			477,000	5,000
Repayments of bank borrowings			(135,500)	(5,000)
Repayments of building loan			(285)
Deferred financing costs			(900)
Equity proceeds from parent			0	0
Net payments for share-based compensation			(752)	(3,127)
Net cash provided by (used in) financing activities			339,563	(3,127)
Effect of exchange rate changes on cash			0	0
Net change in cash and cash equivalents			142,703	(9,564)
Cash and cash equivalents, beginning of period			9,681	72,886
Cash and cash equivalents, end of period	152,384	63,322	152,384	63,322
Guarantor Subsidiary
Cash flows from operating activities:
Net loss	(19,300)	244,245	(243,584)	318,337
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion and amortization	32,530	34,418	121,255	112,627
Write-down of oil and gas properties	36,483	0	268,128	0
Accretion expense	10,024	6,406	29,973	19,041
Deferred income tax provision (benefit)	1,888	(193,059)	10,947	(167,649)
Settlement of asset retirement obligations			(14,129)	(59,811)
Non-cash stock compensation expense			0	0
Non-cash derivative expense			1,261	10,854
Non-cash interest expense			0	0
Other non-cash expense			0
Change in current income taxes			0	0
Non-cash loss from investment in subsidiaries			0	0
Change in intercompany receivables/payables			1,658	(41,056)
(Increase) decrease in accounts receivable			(3,116)	4,317
Increase in other current assets			0	0
(Increase) decrease in inventory				2,415
Increase (decrease) in accounts payable			(4,168)	(4,030)
Decrease in other current liabilities			(298)	102
Other			(718)	(727)
Net cash provided by operating activities			167,209	194,420
Cash flows from investing activities:
Investment in oil and gas properties			(137,196)	(197,471)
Proceeds from sale of oil and gas properties, net of expenses				11,643
Investment in fixed and other assets			0	0
Change in restricted funds			0	0
Investment in subsidiaries			0	0
Net cash used in investing activities			(137,196)	(185,828)
Cash flows from financing activities:
Proceeds from bank borrowings			0	0
Repayments of bank borrowings			0	0
Repayments of building loan			0
Deferred financing costs			0
Equity proceeds from parent			0	0
Net payments for share-based compensation			0	0
Net cash provided by (used in) financing activities			0	0
Effect of exchange rate changes on cash			0	0
Net change in cash and cash equivalents			30,013	8,592
Cash and cash equivalents, beginning of period			2	1,450
Cash and cash equivalents, end of period	30,015	10,042	30,015	10,042
Non- Guarantor Subsidiaries
Cash flows from operating activities:
Net loss	(1)	(32,544)	(12,890)	(90,380)
Adjustments to reconcile net loss to net cash provided by operating activities:
Depreciation, depletion and amortization	0	0	0	0
Write-down of oil and gas properties	0	0	350	45,169
Accretion expense	0	0	0	0
Deferred income tax provision (benefit)	0	16,267	0	0
Settlement of asset retirement obligations			(899)	0
Non-cash stock compensation expense			0	0
Non-cash derivative expense			0	0
Non-cash interest expense			0	0
Other non-cash expense			6,081
Change in current income taxes			0	0
Non-cash loss from investment in subsidiaries			6,445	45,190
Change in intercompany receivables/payables			0	9,736
(Increase) decrease in accounts receivable			(882)	17
Increase in other current assets			33	(40)
(Increase) decrease in inventory				0
Increase (decrease) in accounts payable			0	0
Decrease in other current liabilities			0	0
Other			0	0
Net cash provided by operating activities			(1,762)	9,692
Cash flows from investing activities:
Investment in oil and gas properties			(351)	(10,560)
Proceeds from sale of oil and gas properties, net of expenses				0
Investment in fixed and other assets			0	0
Change in restricted funds			1,046	1,828
Investment in subsidiaries			716	(9,708)
Net cash used in investing activities			1,411	(18,440)
Cash flows from financing activities:
Proceeds from bank borrowings			0	0
Repayments of bank borrowings			0	0
Repayments of building loan			0
Deferred financing costs			0
Equity proceeds from parent			(716)	9,708
Net payments for share-based compensation			0	0
Net cash provided by (used in) financing activities			(716)	9,708
Effect of exchange rate changes on cash			(9)	(2)
Net change in cash and cash equivalents			(1,076)	958
Cash and cash equivalents, beginning of period			1,076	152
Cash and cash equivalents, end of period	$ 0	$ 1,110	$ 0	$ 1,110