INDEBTEDNESS - Revolving credit agreement (Details)		3 Months Ended		9 Months Ended		21 Months Ended
	Oct. 10, 2018 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)	Jul. 02, 2020 USD ($)	Jun. 28, 2020 USD ($)	Jan. 17, 2020 USD ($) installment	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Repayments of lines of credit				$ 40,076,000	$ 18,000,000
Long-term Debt		$ 104,924,000		104,924,000					$ 115,000,000
Amortization of debt financing costs		0	$ 359,000	858,000	637,000
Line of Credit | Revolving Credit Agreement | Letter of Credit
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity		5,000,000		5,000,000
Line of Credit | Revolving Credit Agreement | Revolving Credit Facility
Debt Instrument [Line Items]
Agreement term	5 years
Line of credit facility, maximum borrowing capacity	$ 500,000,000
Line of credit facility, borrowing base	$ 115,000,000							$ 90,000,000
Borrowing base deficiency		7,800,000		$ 7,800,000				$ 25,000,000
Repayments of lines of credit						$ 17,300,000
Line of credit facility, interest rate description				Borrowings under the Revolving Credit Agreement bear interest at a floating rate of either LIBOR or a specified base rate plus a margin of (i) if a new money loan, 6.5% for LIBOR borrowings or 5.5% for specified base rate borrowings or (ii) if a roll-up loan, 5.5% for LIBOR borrowings or 4.5% for specified base rate borrowings.
Line of credit facility, commitment fee percentage	0.50%
Long-term Debt		74,900,000		$ 74,900,000			$ 89,900,000
Amortization of debt financing costs		200,000	$ 100,000	$ 800,000	$ 300,000
Debtor reorganization items, write-off of debt issuance costs		$ 2,000,000
Ratio of total debt to EBITDAX (not more than)	400.00%
Ratio of current assets to current liabilities (not less than)	100.00%
Covenant, borrowing base deficiency, number of equal monthly installments (in installments) | installment								4
Extension term				45 days
Line of Credit | Revolving Credit Agreement | Revolving Credit Facility | Other Current Assets
Debt Instrument [Line Items]
Unamortized debt issuance costs									$ 2,600,000
Roll-up Loans | Revolving Credit Agreement | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	5.50%
Roll-up Loans | Revolving Credit Agreement | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	4.50%
New Money Loans | Revolving Credit Agreement | Revolving Credit Facility | LIBOR
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	6.50%
New Money Loans | Revolving Credit Agreement | Revolving Credit Facility | Base Rate
Debt Instrument [Line Items]
Debt instrument, basis spread on variable rate	5.50%