Condensed Consolidating Financial Information - (Balance Sheet) (Details) - USD ($) $ in Thousands	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013	Dec. 31, 2012
Current assets:
Cash and cash equivalents	$ 208,637	$ 3,252	$ 11,821	$ 6,193
Accounts receivable	35,074	108,110
Prepaid expenses and other current assets	9,699	13,092
Derivative instruments		160,217
Total current assets	253,410	284,671
Property, plant and equipment:
Oil and natural gas properties (full cost method)	4,730,537	4,533,516
Gas gathering and processing equipment	15,811	14,315
Office furniture and fixtures	15,838	14,030
Total property, plant and equipment	4,762,186	4,561,861
Accumulated depletion, depreciation and amortization	(4,253,806)	(2,495,793)
Total property, plant and equipment, net	508,380	2,066,068
Other assets:
Deferred financing costs, net		34,862
Other long-term assets	35,931	6,665
Total other assets	35,931	41,527
Total assets	797,721	2,392,266
Current liabilities:
Accounts payable and accrued liabilities	102,321	339,420
Derivative instruments		4,645
Current maturities of long-term debt, net of discount		1,988,883
Other short-term liabilities	1,161	14,304
Total current liabilities	103,482	2,347,252
Asset retirement obligation	40,860	39,382
Derivative instruments		2,269
Other long-term liabilities	48,197	67,155
Liabilities subject to compromise	2,908,130
Total liabilities	$ 3,100,669	$ 2,456,058
Commitments and contingencies
Total shareholders’ deficit	$ (2,302,948)	$ (63,792)	201,010	200,433
Total liabilities and shareholders’ deficit	797,721	2,392,266
Reportable legal entity | Parent Company Issuer
Current assets:
Cash and cash equivalents	208,636	1,993	10,297	6,139
Accounts receivable	35,074	108,110
Prepaid expenses and other current assets	9,692	12,601
Derivative instruments		160,217
Total current assets	253,402	282,921
Property, plant and equipment:
Oil and natural gas properties (full cost method)	666,697	614,556
Office furniture and fixtures	15,838	14,030
Total property, plant and equipment	682,535	628,586
Accumulated depletion, depreciation and amortization	(521,662)	(85,285)
Total property, plant and equipment, net	160,873	543,301
Other assets:
Deferred financing costs, net		34,862
Investment in subsidiaries	(2,334,109)	(1,130,992)
Due from subsidiaries	2,665,765	2,639,738
Other long-term assets	35,931	6,665
Total other assets	367,587	1,550,273
Total assets	781,862	2,376,495
Current liabilities:
Accounts payable and accrued liabilities	103,940	339,772
Derivative instruments		4,645
Current maturities of long-term debt, net of discount		1,988,883
Other short-term liabilities	1,102	14,236
Total current liabilities	105,042	2,347,536
Asset retirement obligation	24,070	23,983
Derivative instruments		2,269
Other long-term liabilities	47,568	66,499
Liabilities subject to compromise	2,908,130
Total liabilities	$ 3,084,810	$ 2,440,287
Commitments and contingencies
Total shareholders’ deficit	$ (2,302,948)	$ (63,792)
Total liabilities and shareholders’ deficit	781,862	2,376,495
Reportable legal entity | Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	1	1,259	$ 1,524	$ 54
Accounts receivable	1,738	470
Prepaid expenses and other current assets	7	491
Total current assets	1,746	2,220
Property, plant and equipment:
Oil and natural gas properties (full cost method)	4,063,840	3,918,960
Gas gathering and processing equipment	15,811	14,315
Total property, plant and equipment	4,079,651	3,933,275
Accumulated depletion, depreciation and amortization	(3,732,144)	(2,410,508)
Total property, plant and equipment, net	347,507	1,522,767
Other assets:
Total assets	349,253	1,524,987
Current liabilities:
Accounts payable and accrued liabilities	119	118
Other short-term liabilities	59	68
Total current liabilities	178	186
Asset retirement obligation	16,790	15,399
Due to parent	2,665,765	2,639,738
Other long-term liabilities	629	656
Total liabilities	$ 2,683,362	$ 2,655,979
Commitments and contingencies
Total shareholders’ deficit	$ (2,334,109)	$ (1,130,992)
Total liabilities and shareholders’ deficit	349,253	1,524,987
Eliminations
Current assets:
Accounts receivable	(1,738)	(470)
Total current assets	(1,738)	(470)
Other assets:
Investment in subsidiaries	2,334,109	1,130,992
Due from subsidiaries	(2,665,765)	(2,639,738)
Total other assets	(331,656)	(1,508,746)
Total assets	(333,394)	(1,509,216)
Current liabilities:
Accounts payable and accrued liabilities	(1,738)	(470)
Total current liabilities	(1,738)	(470)
Due to parent	(2,665,765)	(2,639,738)
Total liabilities	$ (2,667,503)	$ (2,640,208)
Commitments and contingencies
Total shareholders’ deficit	$ 2,334,109	$ 1,130,992
Total liabilities and shareholders’ deficit	$ (333,394)	$ (1,509,216)