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LONG-TERM DEBT - Schedule of Debt (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Nov. 30, 2019
Debt Instrument [Line Items]
Principal Balance	$ 988,755		$ 988,755		$ 1,127,733
Unamortized debt discounts and premiums	2,276		2,276		4,860
Unamortized debt issuance costs	(7,704)		(7,704)		(14,432)
Total debt	983,327		983,327		1,118,161
Less current portion of long-term debt	(65,000)		(65,000)		0
Total long-term debt	918,327		918,327		1,118,161
Write-off of debt issuance costs	1,543	$ 0	1,543	$ 0
Second Lien Notes due 2023 \| Line of Credit
Debt Instrument [Line Items]
Principal Balance	287,755		287,755		417,733
Unsecured VEN Bakken Note
Debt Instrument [Line Items]
Principal Balance	130,000		130,000		130,000
Revolving Credit Facility
Debt Instrument [Line Items]
Principal Balance	571,000		571,000		580,000
Revolving Credit Facility \| Other Noncurrent Assets, Net
Debt Instrument [Line Items]
Unamortized debt issuance costs	$ (6,900)		$ (6,900)		$ (9,800)
Revolving Credit Facility \| Second Lien Notes due 2023
Debt Instrument [Line Items]
Total debt						$ 200,000