FRESH-START ACCOUNTING-Balance sheet effects (Details) - USD ($) $ in Thousands	Dec. 31, 2018	Dec. 31, 2017	Sep. 09, 2017	Dec. 31, 2016	Sep. 09, 2016	Dec. 31, 2015
Current assets:
Cash and cash equivalents	$ 46,866	$ 424,071		$ 24	$ 13,943
Accounts receivable	35,718	36,416			116,859
Receivables from derivative contracts	57,280	677			97,648
Restricted cash					17,164
Prepaids and other	4,788	10,628			7,629
Total current assets	144,652	471,792			253,243
Oil and natural gas properties (full cost method):
Evaluated	1,470,509	877,316			1,214,129
Unevaluated	971,918	765,786			332,115
Gross oil and natural gas properties	2,442,427	1,643,102			1,546,244
Less - accumulated depletion	(639,951)	(570,155)
Net oil and natural gas properties	1,802,476	1,072,947			1,546,244
Other operating property and equipment:
Other operating property and equipment	130,251	101,282			38,071
Less - accumulated depreciation	(8,388)	(4,092)
Net other operating property and equipment	121,863	97,190			38,071
Other noncurrent assets:
Receivables from derivative contracts	12,437				4,431
Funds in escrow and other	2,181	1,691			1,637
Total assets	2,083,609	1,643,620			1,843,626
Current liabilities:
Accounts payable and accrued liabilities	157,848	131,087			173,688
Liabilities from derivative contracts	3,768	19,248			102
Other					4,849
Current portion of asset retirement obligation	126
Total current liabilities	161,742	150,335			178,639
Long-term debt, net	613,105	409,168			1,016,160
Liabilities subject to compromise					2,007,703
Other noncurrent liabilities:
Liabilities from derivative contracts	9,139	7,751			525
Asset retirement obligations	6,788	4,368			32,156
Other					3,953
Commitments and contingencies
Mezzanine equity:
Redeemable noncontrolling interest					41,070
Stockholders' equity:
Common stock	16	15			9
Additional paid-in capital	1,095,367	1,016,281			571,114
Retained earnings (accumulated deficit)	101,661	55,702
Total stockholders' equity	1,197,044	1,071,998		$ 112,688	571,123
Total liabilities and stockholders' equity	$ 2,083,609	$ 1,643,620			1,843,626
Reorganization Adjustments
Current assets:
Cash and cash equivalents					(97,521)
Total current assets					(97,521)
Other noncurrent assets:
Total assets					(97,521)
Current liabilities:
Accounts payable and accrued liabilities					13,688
Total current liabilities					13,688
Liabilities subject to compromise					(2,007,703)
Other noncurrent liabilities:
Commitments and contingencies
Stockholders' equity:
Common stock					9
Additional paid-in capital					571,114
Retained earnings (accumulated deficit)					4,613,289
Total stockholders' equity					1,896,494
Total liabilities and stockholders' equity					(97,521)
Fresh Start Adjustments
Current assets:
Prepaids and other					(1,332)
Total current assets					(1,332)
Oil and natural gas properties (full cost method):
Evaluated					(6,497,874)
Unevaluated					(861,144)
Gross oil and natural gas properties					(7,359,018)
Less - accumulated depletion					6,803,231
Net oil and natural gas properties					(555,787)
Other operating property and equipment:
Other operating property and equipment					(62,008)
Less - accumulated depreciation					24,154
Net other operating property and equipment					(37,854)
Other noncurrent assets:
Funds in escrow and other					27
Total assets					(594,946)
Current liabilities:
Other					4,435
Total current liabilities					4,435
Long-term debt, net					(14,954)
Other noncurrent liabilities:
Asset retirement obligations					(16,799)
Other					3,425
Commitments and contingencies
Mezzanine equity:
Redeemable noncontrolling interest					(178,821)
Stockholders' equity:
Retained earnings (accumulated deficit)					(392,232)
Total stockholders' equity					(392,232)
Total liabilities and stockholders' equity					(594,946)
Predecessor
Current assets:
Cash and cash equivalents					111,464
Cash and cash equivalents					13,943	$ 8,026
Accounts receivable					116,859
Receivables from derivative contracts					97,648
Restricted cash					17,164
Prepaids and other					8,961
Total current assets					352,096
Oil and natural gas properties (full cost method):
Evaluated					7,712,003
Unevaluated					1,193,259
Gross oil and natural gas properties					8,905,262
Less - accumulated depletion					(6,803,231)
Net oil and natural gas properties					2,102,031
Other operating property and equipment:
Other operating property and equipment					100,079
Less - accumulated depreciation					(24,154)
Net other operating property and equipment					75,925
Other noncurrent assets:
Receivables from derivative contracts					4,431
Funds in escrow and other					1,610
Total assets					2,536,093
Current liabilities:
Accounts payable and accrued liabilities					160,000
Liabilities from derivative contracts					102
Other					414
Total current liabilities					160,516
Long-term debt, net					1,031,114
Liabilities subject to compromise					2,007,703
Other noncurrent liabilities:
Liabilities from derivative contracts					525
Asset retirement obligations					48,955
Other					528
Commitments and contingencies
Mezzanine equity:
Redeemable noncontrolling interest					219,891
Stockholders' equity:
Common stock					12
Additional paid-in capital					3,287,906
Retained earnings (accumulated deficit)					(4,221,057)
Total stockholders' equity					(933,139)	$ 52,414
Total liabilities and stockholders' equity					2,536,093
Predecessor | Reorganization Adjustments
Stockholders' equity:
Common stock					(12)
Additional paid-in capital					(3,287,906)
Total stockholders' equity					$ 3,287,918