OTHER DEFERRED CREDITS AND OTHER LIABILITIES (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2015	Mar. 31, 2024	Dec. 31, 2023
Deferred credits and other liabilities
Transmission easements		$ 17,949	$ 17,862
OATT deposits		29,707	27,872
Financial liabilities - reclamation		13,128	16,895
Customer deposits		12,079	12,091
Contract liabilities (unearned revenue) - noncurrent		2,998	3,125
Operating lease liabilities - noncurrent		1,312	1,396
Other		4,437	4,884
Total other deferred credits and other liabilities		81,610	$ 84,125
Transmission Right of Way Easements
Deferred credits and other liabilities
Total due for easement right of way	$ 26,800
Transmission Right of Way Easements | Other Deferred Credits and Other Liabilities
Deferred credits and other liabilities
Transmission easements		$ 17,900