Supplemental Guarantor Information - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Current assets:
Cash and cash equivalents	$ 70,236	$ 85,414	$ 23,666	$ 15,800
Receivables:
Oil and natural gas sales	43,073	35,005
Joint interest and other	63,928	22,012
Total receivables	107,001	57,017
Prepaid expenses and other assets	14,504	26,879
Total current assets	191,741	169,310
Property and equipment - at cost:
Oil and natural gas properties and equipment (full cost method, of which $0 at December 31, 2016 and $18,595 at December 31, 2015 were excluded from amortization)	7,932,504	7,902,494
Furniture, fixtures and other	20,898	20,802
Total property and equipment	7,953,402	7,923,296
Less accumulated depreciation, depletion and amortization	7,406,349	6,933,247
Net property and equipment	547,053	990,049
Deferred income taxes		27,595
Restricted deposits for asset retirement obligations	27,371	15,606
Income tax receivables	52,097
Other assets	11,464	5,462
Total assets	829,726	1,208,022
Current liabilities:
Accounts payable	81,039	109,797
Undistributed oil and natural gas proceeds	26,254	21,439
Asset retirement obligations	78,264	84,335
Long-term debt	8,272
Accrued liabilities	9,200	11,922
Total current liabilities	203,029	227,493
Long-term debt, less current maturities	1,012,455	1,196,855
Asset retirement obligations, less current portion	256,174	293,987
Other liabilities	17,105	16,178
Shareholders’ equity (deficit):
Common stock, $0.00001 par value; 200,000,000 shares authorized; 140,543,545 issued and 137,674,372 outstanding at December 31, 2016; 79,375,662 issued and 76,506,489 outstanding at December 31, 2015	1	1
Additional paid-in capital	539,973	423,499
Retained earnings (deficit)	(1,174,844)	(925,824)
Treasury stock, at cost; 2,869,173 shares at December 31, 2016 and 2015	(24,167)	(24,167)
Total shareholders’ equity (deficit)	(659,037)	(526,491)	509,308	540,610
Total liabilities and shareholders’ equity (deficit)	829,726	1,208,022
Parent Company
Current assets:
Cash and cash equivalents	70,236	85,414	$ 23,666	$ 15,800
Receivables:
Oil and natural gas sales	2,173	2,742
Joint interest and other	163,200	121,190
Total receivables	165,373	123,932
Prepaid expenses and other assets	12,448	25,375
Total current assets	248,057	234,721
Property and equipment - at cost:
Oil and natural gas properties and equipment (full cost method, of which $0 at December 31, 2016 and $18,595 at December 31, 2015 were excluded from amortization)	5,700,205	5,682,793
Furniture, fixtures and other	20,898	20,802
Total property and equipment	5,721,103	5,703,595
Less accumulated depreciation, depletion and amortization	5,360,137	5,258,563
Net property and equipment	360,966	445,032
Deferred income taxes		27,251
Restricted deposits for asset retirement obligations	27,371	15,606
Income tax receivables	52,097
Other assets	394,931	498,782
Total assets	1,083,422	1,221,392
Current liabilities:
Accounts payable	74,306	100,282
Undistributed oil and natural gas proceeds	24,493	20,463
Asset retirement obligations	62,261	63,716
Long-term debt	8,272
Accrued liabilities	9,293	11,922
Total current liabilities	178,625	196,383
Long-term debt, less current maturities	1,012,455	1,196,855
Asset retirement obligations, less current portion	142,376	173,105
Other liabilities	408,050	329,129
Shareholders’ equity (deficit):
Common stock, $0.00001 par value; 200,000,000 shares authorized; 140,543,545 issued and 137,674,372 outstanding at December 31, 2016; 79,375,662 issued and 76,506,489 outstanding at December 31, 2015	1	1
Additional paid-in capital	539,973	423,499
Retained earnings (deficit)	(1,173,891)	(1,073,413)
Treasury stock, at cost; 2,869,173 shares at December 31, 2016 and 2015	(24,167)	(24,167)
Total shareholders’ equity (deficit)	(658,084)	(674,080)
Total liabilities and shareholders’ equity (deficit)	1,083,422	1,221,392
Guarantor Subsidiaries
Receivables:
Oil and natural gas sales	40,900	32,263
Total receivables	40,900	32,263
Prepaid expenses and other assets	2,056	1,504
Total current assets	42,956	33,767
Property and equipment - at cost:
Oil and natural gas properties and equipment (full cost method, of which $0 at December 31, 2016 and $18,595 at December 31, 2015 were excluded from amortization)	2,232,299	2,219,701
Total property and equipment	2,232,299	2,219,701
Less accumulated depreciation, depletion and amortization	2,045,259	1,822,273
Net property and equipment	187,040	397,428
Deferred income taxes		344
Other assets	344,742	266,748
Total assets	574,738	698,287
Current liabilities:
Accounts payable	6,733	9,515
Undistributed oil and natural gas proceeds	1,761	976
Asset retirement obligations	16,003	20,619
Accrued liabilities	99,179	99,178
Total current liabilities	123,676	130,288
Asset retirement obligations, less current portion	113,798	120,882
Shareholders’ equity (deficit):
Additional paid-in capital	704,885	704,885
Retained earnings (deficit)	(367,621)	(257,768)
Total shareholders’ equity (deficit)	337,264	447,117
Total liabilities and shareholders’ equity (deficit)	574,738	698,287
Eliminations
Receivables:
Joint interest and other	(99,272)	(99,178)
Total receivables	(99,272)	(99,178)
Total current assets	(99,272)	(99,178)
Property and equipment - at cost:
Less accumulated depreciation, depletion and amortization	953	(147,589)
Net property and equipment	(953)	147,589
Other assets	(728,209)	(760,068)
Total assets	(828,434)	(711,657)
Current liabilities:
Accrued liabilities	(99,272)	(99,178)
Total current liabilities	(99,272)	(99,178)
Other liabilities	(390,945)	(312,951)
Shareholders’ equity (deficit):
Additional paid-in capital	(704,885)	(704,885)
Retained earnings (deficit)	366,668	405,357
Total shareholders’ equity (deficit)	(338,217)	(299,528)
Total liabilities and shareholders’ equity (deficit)	$ (828,434)	$ (711,657)