OTHER DEFERRED CREDITS AND OTHER LIABILITIES - Summary (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023
Deferred Credits and Other Liabilities [Abstract]
Transmission easements	$ 17,949	$ 17,862
OATT deposits	38,059	27,872
Financial liabilities - reclamation	12,564	16,895
Customer deposits	13,251	12,091
Contract liabilities (unearned revenue) - noncurrent	2,871	3,125
Operating lease liabilities - noncurrent	5,461	1,396
Other	4,468	4,884
Total other deferred credits and other liabilities	$ 94,623	$ 84,125