ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Before and After Tax Amounts by Component (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Change in unrealized gain (loss) on securities:
Change in net unrealized gain (loss) during the period	$ (138,630)	$ (28,865)	$ 16,432
Reclassification adjustment for net gains included in net gain on sale of securities and other assets		(1,207)	(4,592)
Accretion of net unrealized loss on securities transferred to held-to-maturity	2,953
Net change	(135,677)	(30,072)	11,840
Tax benefit	(42,671)	(9,514)	3,767
Net change in unrealized gain (loss) on securities, net of reclassification adjustments and tax	(93,006)	(20,558)	8,073
Change in pension and other postretirement obligations:
Reclassification adjustment for expense included in other expense	(3,715)	(1,092)	(1,272)
Reclassification adjustment for curtailment loss		1,543	(1,651)
Change in the net actuarial gain	(2,062)	6,563	2,817
Net change	(5,777)	7,014	(106)
Tax expense	(1,817)	2,234	(44)
Net change in pension and other postretirement obligations	(3,960)	4,780	(62)
Change in unrealized gain (loss) on derivatives:
Change in net unrealized gain (loss) during the period	14,412	5,277	(24,449)
Reclassification adjustment for loss included in loss on termination of derivatives		16,505	6,596
Reclassification adjustment for expense included in interest expense	(1,621)	940	6,127
Net change	12,791	22,722	(11,726)
Tax expense	4,023	7,201	(3,731)
Net change in unrealized gain (loss) on derivatives, net of reclassification adjustments and tax	8,768	15,521	(7,995)
Total other comprehensive (loss) income, net of tax	$ (88,198)	$ (257)	$ 16