ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Accumulated Other Comprehensive Income (Loss) [Line Items]
Amortization of net (gain) loss	$ 1,442			$ 490			$ 4,326	$ 1,470
Amortization of unrecognized prior service cost	93			131			279	393
Reclassification adjustment, before tax and regulatory adjustments	1,535			621			4,605	1,863
Regulatory adjustments	(1,536)			(620)			(4,607)	(1,862)
Other Comprehensive Income (Loss), Defined Benefit Plan, Gain (Loss), Reclassification Adjustment from AOCI, before Tax	(1)			1			(2)	1
OCI, Debt Securities, Available-for-Sale, Unrealized Holding Gain (Loss), before Adjustment and Tax	324			0			322	0
Realized Investment Gains (Losses)	(1)			0			(11)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax	1			0			11	0
Other comprehensive (income) loss, available-for-sale securities, after reclassification adjustment, before tax	324			0			322	0
Other Comprehensive Income (Loss), before Tax	323			1			320	1
Other Comprehensive Income (Loss), Tax	(68)			0			(67)	0
Other comprehensive income	$ 255	$ 8	$ (10)	$ (1)	$ 0	$ 0	$ 253	$ (1)