ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Change in unrealized holding gain or loss on securities:
Change in net unrealized gain or loss during the period	$ (28,865)	$ 16,432	$ 9,693
Reclassification adjustment for net gains included in net gain on securities and other assets	(1,207)	(4,592)	(31)
Net change	(30,072)	11,840	9,662
Tax (benefit) expense	(9,514)	3,767	3,084
Net change in unrealized holding gain or loss on securities, net of reclassification adjustments and tax	(20,558)	8,073	6,578
Change in pension and other postretirement obligations:
Reclassification adjustment for expense included in other expense	(1,092)	(1,272)	729
Reclassification adjustment for curtailment loss	1,543	(1,651)
Change in the net actuarial gain or loss	6,563	2,817	(296)
Net change	7,014	(106)	433
Tax expense	2,234	(44)	167
Net change in pension and other postretirement obligations	4,780	(62)	266
Change in unrealized gain or loss on derivatives:
Change in net unrealized gain or loss during the period	5,277	(24,449)	(8,254)
Reclassification adjustment for loss included in loss on termination of derivatives	16,505	6,596
Reclassification adjustment for expense included in interest expense	940	6,127	(955)
Net change	22,722	(11,726)	(9,209)
Tax expense (benefit)	7,201	(3,731)	(2,925)
Net change in unrealized gain or loss on derivatives, net of reclassification adjustments and tax	15,521	(7,995)	(6,284)
Total other comprehensive (loss) income, net of tax	$ (257)	$ 16	$ 560