COMMITMENTS AND CONTINGENCIES (Schedule of Firm Sales Contracted with Third Parties) (Details) MMBTU in Thousands	Jun. 30, 2021 MMBTU
Commitments and Contingencies Disclosure [Abstract]
Remaining 2021 (MMBtu per day)	16
2022 (MMBtu per day)	4
2023 (MMBtu per day)	0
2024 (MMBtu per day)	0
2025 (MMBtu per day)	0
Thereafter (MMBtu per day)	0