FRESH-START ACCOUNTING - Balance sheet effects (Details) - USD ($) $ in Thousands	Dec. 31, 2019	Oct. 02, 2019	Oct. 01, 2019	Sep. 30, 2019	Jan. 01, 2019	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Current assets:
Cash and cash equivalents			$ 17,009
Cash and cash equivalents	$ 5,701	$ 15,546	15,546			$ 46,866
Accounts receivable, net	48,504	37,826	37,826			35,718
Assets from derivative contracts	4,995	15,310	15,310			57,280
Restricted cash		13,839
Prepaids and other	7,379	10,290	14,642			4,788
Total current assets	71,153	92,811	84,787			144,652
Oil and natural gas properties (full cost method):
Evaluated	420,609	380,364	2,155,288			1,470,509
Unevaluated	105,009	108,954	438,365			971,918
Gross oil and natural gas properties	525,618	489,318	2,593,653			2,442,427
Less - accumulated depletion	(19,474)		(1,709,719)			(639,951)
Net oil and natural gas properties	506,144	489,318	883,934			1,802,476
Other operating property and equipment:
Other operating property and equipment	3,655	3,655	203,373			130,251
Less - accumulated depreciation	(378)		(14,416)			(8,388)
Net other operating property and equipment	3,277	3,655	188,957			121,863
Other noncurrent assets:
Assets from derivative contracts	224	4,120	4,120			12,437
Operating lease right of use assets	3,165	3,394	3,694		$ 5,462
Funds in escrow and other	703	1,138	1,138			2,181
Other	123					1,611
Total assets	584,666	594,436	1,166,630			2,083,609
Current liabilities:
Accounts payable and accrued liabilities	97,333	115,305	112,578		157,763	157,848
Liabilities from derivative contracts	8,069	6,829	6,829			3,768
Current portion of long-term debt, net			258,234
Operating lease liabilities	923	913	1,337		2,103
Asset retirement obligations	109					126
Total current liabilities	106,434	123,047	378,978			161,742
Long-term debt, net	144,000	130,000				613,105
Liabilities subject to compromise			625,005
Other noncurrent liabilities:
Liabilities from derivative contracts	4,854	1,625	1,625			9,139
Asset retirement obligations	10,481	10,153	10,153			6,788
Operating lease liabilities	2,247	2,482	2,438		$ 3,444
Commitments and contingencies
Stockholders' equity:
Common stock	2	2	16			16
Additional paid-in capital	327,108	327,127	1,087,441			1,095,367
Retained earnings (accumulated deficit)	(10,460)		(939,026)			101,661
Total stockholders' equity	316,650	327,129	148,431	$ 30,477		1,197,044	$ 1,071,998	$ 112,688
Total liabilities and stockholders' equity	584,666	$ 594,436	1,166,630			$ 2,083,609
Reorganization Adjustments
Current assets:
Cash and cash equivalents			(1,463)
Restricted cash			13,839
Prepaids and other			7,110
Total current assets			19,486
Other noncurrent assets:
Total assets			19,486
Current liabilities:
Accounts payable and accrued liabilities			2,727
Current portion of long-term debt, net			(258,234)
Total current liabilities			(255,507)
Long-term debt, net			130,000
Liabilities subject to compromise			(625,005)
Other noncurrent liabilities:
Commitments and contingencies
Stockholders' equity:
Common stock	2		(16)
Additional paid-in capital	$ 327,127		(1,087,441)
Retained earnings (accumulated deficit)			1,530,326
Total stockholders' equity			769,998
Total liabilities and stockholders' equity			19,486
Fresh Start Adjustments
Current assets:
Prepaids and other			(11,462)
Total current assets			(11,462)
Oil and natural gas properties (full cost method):
Evaluated			(1,774,924)
Unevaluated			(329,411)
Gross oil and natural gas properties			(2,104,335)
Less - accumulated depletion			1,709,719
Net oil and natural gas properties			(394,616)
Other operating property and equipment:
Other operating property and equipment			(199,718)
Less - accumulated depreciation			14,416
Net other operating property and equipment			(185,302)
Other noncurrent assets:
Operating lease right of use assets			(300)
Total assets			(591,680)
Current liabilities:
Operating lease liabilities			(424)
Total current liabilities			(424)
Other noncurrent liabilities:
Operating lease liabilities			44
Commitments and contingencies
Stockholders' equity:
Retained earnings (accumulated deficit)			(591,300)
Total stockholders' equity			(591,300)
Total liabilities and stockholders' equity			$ (591,680)