LEASES - Components of lease costs and other information (Details) $ in Thousands	12 Months Ended
	Dec. 31, 2019 USD ($)
Lease, Cost [Abstract]
Fixed lease costs	$ 5,084
Short-term lease costs	1,096
Variable lease costs	575
Total lease costs	6,755
Lessee, Lease, Description [Line Items]
Lease cost	6,755
Cash paid for amounts included in the measurement of operating lease liabilities:
Operating cash flows from operating leases	222
Investing cash flows from operating leases	$ 4,768
Lease term and discount rate
Weighted-average remaining lease term (years)	4 years 5 months 12 days
Weighted-average discount rate	5.30%
General and administrative
Lease, Cost [Abstract]
Total lease costs	$ 474
Lessee, Lease, Description [Line Items]
Lease cost	474
Total lease costs expensed
Lease, Cost [Abstract]
Total lease costs	1,067
Lessee, Lease, Description [Line Items]
Lease cost	1,067
Oil sales | Production costs
Lease, Cost [Abstract]
Total lease costs	593
Lessee, Lease, Description [Line Items]
Lease cost	593
Oil and Gas Properties
Lease, Cost [Abstract]
Total lease costs	5,688
Lessee, Lease, Description [Line Items]
Lease cost	$ 5,688