CHAPTER 11 PROCEEDINGS (Cash Flows) (Details) - USD ($) $ in Thousands	1 Months Ended	11 Months Ended	12 Months Ended
	Feb. 08, 2018	Dec. 31, 2018	Dec. 31, 2019
Cash flows from operating activities:
Net income (loss)	$ (14,862)	$ (3,249,347)	$ (929,622)
Adjustments to reconcile net loss to cash from operating activities:
Depreciation, depletion and amortization	12,554	160,942	132,292
Non-cash lease expense	0	0	3,122
Provision for uncollectible receivables	0	22,438	3,528
Impairment of assets	5,560	3,205,051	905,293
Non-cash reorganization items, net	0	0	(26,160)
Amortization of deferred financing costs	171	526	658
Amortization of debt premium	0	(4,512)	(3,432)
Equity-based compensation expense	0	22,025	6,412
Non-cash exploration expense	4,575	26,055	43,412
(Gain) loss on derivatives	(6,663)	10,247	11,744
Cash settlements of derivatives	(2,296)	(38,961)	7,642
Cash paid for derivatives	0	0	(1,906)
Impact on cash from changes in:
Accounts receivable	(21,184)	18,011	26,323
Other receivables	(662)	(4,045)	4,988
Related party receivables	(117)	(11,468)	145
Prepaid expenses and other assets	(591)	11,149	(29,078)
Advances from related party	24,116	(37,668)	(6,664)
Settlement of asset retirement obligations	(63)	(1,610)	(234)
Accounts payable, accrued liabilities and other liabilities	23,857	(41,463)	4,216
Operating lease obligations	0	0	(2,771)
Cash from operating activities	26,336	86,809	143,798
Cash flows from investing activities:
Capital expenditures	(36,695)	(762,760)	(327,567)
Cash from investing activities	(37,913)	(560,547)	(320,329)
Cash flows from financing activities:
Proceeds from long-term debt borrowings	60,000	431,500	254,362
Repayments of long-term debt	(43,000)	(273,565)	(9,496)
Payment of taxes withheld on equity-based compensation awards	0	0	(142)
Cash from financing activities	16,932	501,205	244,724
Net increase in cash, cash equivalents and restricted cash	5,355	27,467	68,193
Cash, cash equivalents and restricted cash, beginning of period	4,990	10,345	27,855
Cash, cash equivalents and restricted cash, end of period	$ 10,345	27,855	96,048
Debtor-In-Possession
Cash flows from operating activities:
Net income (loss)			(610,082)
Adjustments to reconcile net loss to cash from operating activities:
Depreciation, depletion and amortization			120,617
Non-cash lease expense			2,981
Provision for uncollectible receivables			1,218
Impairment of assets			556,427
Non-cash reorganization items, net			(26,160)
Amortization of deferred financing costs			195
Amortization of debt premium			(3,432)
Equity-based compensation expense			5,718
Non-cash exploration expense			43,412
(Gain) loss on derivatives			11,744
Cash settlements of derivatives			7,642
Cash paid for derivatives			(1,906)
Impact on cash from changes in:
Accounts receivable			18,783
Other receivables			4,957
Related party receivables			3,651
Prepaid expenses and other assets			(25,716)
Advances from related party			(6,647)
Settlement of asset retirement obligations			(234)
Accounts payable, accrued liabilities and other liabilities			22,373
Operating lease obligations			(2,636)
Cash from operating activities			122,905
Cash flows from investing activities:
Capital expenditures			(249,955)
Distribution received from subsidiary			691
Cash from investing activities			(249,264)
Cash flows from financing activities:
Proceeds from long-term debt borrowings			199,362
Repayments of long-term debt			(4,496)
Payment of taxes withheld on equity-based compensation awards			(142)
Cash from financing activities			194,724
Net increase in cash, cash equivalents and restricted cash			68,365
Cash, cash equivalents and restricted cash, beginning of period			13,985
Cash, cash equivalents and restricted cash, end of period		$ 13,985	$ 82,350