COMPREHENSIVE INCOME (LOSS) - Components (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
COMPREHENSIVE INCOME (LOSS)
Unrealized holding gains (losses) on available-for-sale debt securities	$ 8,993	$ (32,025)
Unrealized holding gains (losses) on available-for-sale debt securities, Income Tax Effect	(1,888)	6,726
Unrealized holding gains (losses) on available-for-sale debt securities, Net of Tax Amount	7,105	(25,299)
Reclassification adjustment for (gains) realized in income	(7)	(2)
Reclassification adjustment for (gains) losses realized in income, Income Tax Effect	1	0
Reclassification adjustment for (gains) losses realized in income. Net of Tax Amount	(6)	(2)
Other comprehensive income (loss) from available-for-sale debt securities, Before-Tax Amount	8,986	(32,027)
Other comprehensive income (loss) on available-for-sale debt securities, Income tax effect	(1,887)	6,726
Other comprehensive income (loss) from available-for-sale debt securities, Net-of-Tax Amount	7,099	(25,301)
Changes from plan amendments and actuarial gains and losses, Before-Tax Amount	(8)	133
Changes from plan amendments and actuarial gains and losses, Income Tax Effect	1	(27)
Changes from plan amendments and actuarial gains and losses, Net-of-Tax Amount	(7)	106
Amortization of prior service cost and net actuarial loss included in net periodic benefit cost, Before-Tax Amount	(14)	(11)
Amortization of prior service cost and net actuarial loss included in net periodic benefit cost, Income Tax Effect	3	2
Amortization of prior service cost and net actuarial loss included in net periodic benefit cost, Net-of-Tax Amount	(11)	(9)
Other comprehensive (loss) income on pension and postretirement obligations	(22)	122
Other comprehensive income (loss) on unfunded retirement obligations, Income Tax Effect	4	(25)
Other comprehensive income (loss) on unfunded retirement obligations, Net-of-Tax Amount	(18)	97
Other comprehensive income (loss) before income tax	8,964	(31,905)
Total other comprehensive income (loss), Income Tax Effect	(1,883)	6,701
Total other comprehensive income (loss), Net-of-Tax Amount	$ 7,081	$ (25,204)