Condensed Consolidating Financial Information - (Balance Sheet) (Details) - USD ($) $ in Thousands	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 170,379	$ 208,637	$ 305,616	$ 3,252
Accounts receivable	22,693	35,074
Prepaid expenses and other current assets	10,218	9,699
Total current assets	203,290	253,410
Property, plant and equipment:
Oil and natural gas properties (full cost method)	4,739,021	4,730,537
Gas gathering and processing equipment	15,812	15,811
Office furniture and fixtures	16,002	15,838
Total property, plant and equipment	4,770,835	4,762,186
Accumulated depletion, depreciation and amortization	(4,359,776)	(4,253,806)
Total property, plant and equipment, net	411,059	508,380
Other assets:
Other long-term assets	35,887	35,931
Total other assets	35,887	35,931
Total assets	650,236	797,721
Current liabilities:
Accounts payable and accrued liabilities	88,175	102,321
Other short-term liabilities	1,263	1,161
Total current liabilities	89,438	103,482
Asset retirement obligation	41,392	40,860
Other long-term liabilities	48,316	48,197
Liabilities subject to compromise	2,908,538	2,908,130
Total liabilities	$ 3,087,684	$ 3,100,669
Commitments and contingencies
Total shareholders’ deficit	$ (2,437,448)	$ (2,302,948)		(63,792)
Total liabilities and shareholders’ deficit	650,236	797,721
Reportable legal entity | Parent Company Issuer
Current assets:
Cash and cash equivalents	170,379	208,636	304,330	1,993
Accounts receivable	22,698	35,074
Prepaid expenses and other current assets	9,784	9,692
Total current assets	202,861	253,402
Property, plant and equipment:
Oil and natural gas properties (full cost method)	671,929	666,697
Office furniture and fixtures	16,002	15,838
Total property, plant and equipment	687,931	682,535
Accumulated depletion, depreciation and amortization	(558,336)	(521,662)
Total property, plant and equipment, net	129,595	160,873
Other assets:
Investment in subsidiaries	(2,391,295)	(2,334,109)
Due from subsidiaries	2,657,539	2,665,765
Other long-term assets	35,887	35,931
Total other assets	302,131	367,587
Total assets	634,587	781,862
Current liabilities:
Accounts payable and accrued liabilities	90,293	103,940
Other short-term liabilities	1,202	1,102
Total current liabilities	91,495	105,042
Asset retirement obligation	24,310	24,070
Other long-term liabilities	47,693	47,568
Liabilities subject to compromise	2,908,537	2,908,130
Total liabilities	$ 3,072,035	$ 3,084,810
Commitments and contingencies
Total shareholders’ deficit	$ (2,437,448)	$ (2,302,948)
Total liabilities and shareholders’ deficit	634,587	781,862
Reportable legal entity | Guarantor Subsidiaries
Current assets:
Cash and cash equivalents		1	$ 1,286	$ 1,259
Accounts receivable	2,232	1,738
Prepaid expenses and other current assets	434	7
Total current assets	2,666	1,746
Property, plant and equipment:
Oil and natural gas properties (full cost method)	4,067,092	4,063,840
Gas gathering and processing equipment	15,812	15,811
Total property, plant and equipment	4,082,904	4,079,651
Accumulated depletion, depreciation and amortization	(3,801,440)	(3,732,144)
Total property, plant and equipment, net	281,464	347,507
Other assets:
Total assets	284,130	349,253
Current liabilities:
Accounts payable and accrued liabilities	119	119
Other short-term liabilities	61	59
Total current liabilities	180	178
Asset retirement obligation	17,082	16,790
Due to parent	2,657,539	2,665,765
Other long-term liabilities	623	629
Liabilities subject to compromise	1
Total liabilities	$ 2,675,425	$ 2,683,362
Commitments and contingencies
Total shareholders’ deficit	$ (2,391,295)	$ (2,334,109)
Total liabilities and shareholders’ deficit	284,130	349,253
Eliminations
Current assets:
Accounts receivable	(2,237)	(1,738)
Total current assets	(2,237)	(1,738)
Other assets:
Investment in subsidiaries	2,391,295	2,334,109
Due from subsidiaries	(2,657,539)	(2,665,765)
Total other assets	(266,244)	(331,656)
Total assets	(268,481)	(333,394)
Current liabilities:
Accounts payable and accrued liabilities	(2,237)	(1,738)
Total current liabilities	(2,237)	(1,738)
Due to parent	(2,657,539)	(2,665,765)
Total liabilities	$ (2,659,776)	$ (2,667,503)
Commitments and contingencies
Total shareholders’ deficit	$ 2,391,295	$ 2,334,109
Total liabilities and shareholders’ deficit	$ (268,481)	$ (333,394)