Guarantor Financial Statements - Condensed Consolidating Balance Sheet (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Jul. 01, 2016	Dec. 31, 2015	Sep. 30, 2015	Dec. 31, 2014
Current assets:
Cash and cash equivalents	$ 182,399		$ 10,759	$ 74,474	$ 74,488
Accounts receivable	44,063		48,031
Fair value of derivative contracts	6,261		38,576
Current income tax receivable	19,863		46,174
Other current assets	11,176		6,881
Total current assets	263,762		150,421
Oil and gas properties, full cost method:
Proved	9,564,561		9,375,898
Less: accumulated DD&A	(9,054,069)		(8,603,955)
Net proved oil and gas properties	510,492		771,943
Unevaluated	404,226		440,043
Other property and equipment, net	27,227		29,289
Other assets, net	29,800		18,473
Investment in subsidiary	0		0
Total assets	1,235,507		1,410,169
Current liabilities:
Accounts payable to vendors	29,259		82,207
Undistributed oil and gas proceeds	7,439		5,992
Accrued interest	22,917		9,022
Asset retirement obligations	60,223		21,291
Current portion of long-term debt	292,795		0
Other current liabilities	10,903		40,712
Total current liabilities	423,536		159,224
Long-term debt	1,122,945		1,060,955
Asset retirement obligations	182,816		204,575
Other long-term liabilities	25,871		25,204
Total liabilities	1,755,168		1,449,958
Commitments and contingencies
Stockholders’ equity:
Common stock	56		55
Treasury stock	(860)		(860)
Additional paid-in capital	1,657,028		1,648,687
Accumulated deficit	(2,179,803)		(1,705,623)
Accumulated other comprehensive income (loss)	3,918		17,952
Total stockholders’ equity	(519,661)	$ 50,000	(39,789)
Total liabilities and stockholders’ equity	1,235,507		1,410,169
Eliminations
Current assets:
Cash and cash equivalents	0		0	0	0
Accounts receivable	(14,892)		(1,756)
Fair value of derivative contracts	0		0
Current income tax receivable	0		0
Other current assets	0		0
Total current assets	(14,892)		(1,756)
Oil and gas properties, full cost method:
Proved	0		0
Less: accumulated DD&A	0		0
Net proved oil and gas properties	0		0
Unevaluated	0		0
Other property and equipment, net	0		0
Other assets, net	0		0
Investment in subsidiary	(480,971)		(746,121)
Total assets	(495,863)		(747,877)
Current liabilities:
Accounts payable to vendors	(14,893)		(1,757)
Undistributed oil and gas proceeds	0		0
Accrued interest	0		0
Asset retirement obligations	0		0
Current portion of long-term debt	0
Other current liabilities	0		0
Total current liabilities	(14,893)		(1,757)
Long-term debt	0		0
Asset retirement obligations	0		0
Other long-term liabilities	0		0
Total liabilities	(14,893)		(1,757)
Commitments and contingencies
Stockholders’ equity:
Common stock	0		0
Treasury stock	0		0
Additional paid-in capital	(1,453,656)		(1,454,372)
Accumulated deficit	976,604		720,130
Accumulated other comprehensive income (loss)	(3,918)		(11,878)
Total stockholders’ equity	(480,970)		(746,120)
Total liabilities and stockholders’ equity	(495,863)		(747,877)
Parent
Current assets:
Cash and cash equivalents	152,384		9,681	63,322	72,886
Accounts receivable	17,336		10,597
Fair value of derivative contracts	0		0
Current income tax receivable	19,863		46,174
Other current assets	11,176		6,848
Total current assets	200,759		73,300
Oil and gas properties, full cost method:
Proved	1,932,435		1,875,152
Less: accumulated DD&A	(1,932,640)		(1,874,622)
Net proved oil and gas properties	(205)		530
Unevaluated	261,101		253,308
Other property and equipment, net	27,227		29,289
Other assets, net	28,852		16,612
Investment in subsidiary	480,971		745,033
Total assets	998,705		1,118,072
Current liabilities:
Accounts payable to vendors	35,189		16,063
Undistributed oil and gas proceeds	6,535		5,216
Accrued interest	22,917		9,022
Asset retirement obligations	0		0
Current portion of long-term debt	292,795
Other current liabilities	10,778		40,161
Total current liabilities	368,214		70,462
Long-term debt	1,122,945		1,060,955
Asset retirement obligations	1,336		1,240
Other long-term liabilities	25,871		25,204
Total liabilities	1,518,366		1,157,861
Commitments and contingencies
Stockholders’ equity:
Common stock	56		55
Treasury stock	(860)		(860)
Additional paid-in capital	1,657,028		1,648,687
Accumulated deficit	(2,179,803)		(1,705,623)
Accumulated other comprehensive income (loss)	3,918		17,952
Total stockholders’ equity	(519,661)		(39,789)
Total liabilities and stockholders’ equity	998,705		1,118,072
Guarantor Subsidiary
Current assets:
Cash and cash equivalents	30,015		2	10,042	1,450
Accounts receivable	40,736		39,190
Fair value of derivative contracts	6,261		38,576
Current income tax receivable	0		0
Other current assets	0		0
Total current assets	77,012		77,768
Oil and gas properties, full cost method:
Proved	7,586,930		7,458,262
Less: accumulated DD&A	(7,076,233)		(6,686,849)
Net proved oil and gas properties	510,697		771,413
Unevaluated	143,125		186,735
Other property and equipment, net	0		0
Other assets, net	948		826
Investment in subsidiary	0		0
Total assets	731,782		1,036,742
Current liabilities:
Accounts payable to vendors	8,963		67,901
Undistributed oil and gas proceeds	904		776
Accrued interest	0		0
Asset retirement obligations	60,223		20,400
Current portion of long-term debt	0
Other current liabilities	125		551
Total current liabilities	70,215		89,628
Long-term debt	0		0
Asset retirement obligations	181,480		203,335
Other long-term liabilities	0		0
Total liabilities	251,695		292,963
Commitments and contingencies
Stockholders’ equity:
Common stock	0		0
Treasury stock	0		0
Additional paid-in capital	1,344,577		1,344,577
Accumulated deficit	(868,408)		(624,824)
Accumulated other comprehensive income (loss)	3,918		24,026
Total stockholders’ equity	480,087		743,779
Total liabilities and stockholders’ equity	731,782		1,036,742
Non- Guarantor Subsidiaries
Current assets:
Cash and cash equivalents	0		1,076	$ 1,110	$ 152
Accounts receivable	883		0
Fair value of derivative contracts	0		0
Current income tax receivable	0		0
Other current assets	0		33
Total current assets	883		1,109
Oil and gas properties, full cost method:
Proved	45,196		42,484
Less: accumulated DD&A	(45,196)		(42,484)
Net proved oil and gas properties	0		0
Unevaluated	0		0
Other property and equipment, net	0		0
Other assets, net	0		1,035
Investment in subsidiary	0		1,088
Total assets	883		3,232
Current liabilities:
Accounts payable to vendors	0		0
Undistributed oil and gas proceeds	0		0
Accrued interest	0		0
Asset retirement obligations	0		891
Current portion of long-term debt	0
Other current liabilities	0		0
Total current liabilities	0		891
Long-term debt	0		0
Asset retirement obligations	0		0
Other long-term liabilities	0		0
Total liabilities	0		891
Commitments and contingencies
Stockholders’ equity:
Common stock	0		0
Treasury stock	0		0
Additional paid-in capital	109,079		109,795
Accumulated deficit	(108,196)		(95,306)
Accumulated other comprehensive income (loss)	0		(12,148)
Total stockholders’ equity	883		2,341
Total liabilities and stockholders’ equity	$ 883		$ 3,232