ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 591,995	$ 562,063	$ 568,887	$ 704,906
Net current period other comprehensive (loss) income	(50,466)	(63,195)	(39,188)	(237,822)
Ending balance	557,184	519,220	557,184	519,220
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(177,645)	(158,534)	(188,923)	16,093
Other comprehensive income (loss) before reclassification	(50,900)	(63,620)	(40,407)	(238,689)
Amounts reclassified from accumulated other comprehensive income (loss)	434	425	1,219	867
Net current period other comprehensive (loss) income	(50,466)	(63,195)	(39,188)	(237,822)
Ending balance	(228,111)	(221,729)	(228,111)	(221,729)
Unrealized Gains and Losses on Available- for-Sales Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(176,898)	(157,625)	(188,154)	17,056
Other comprehensive income (loss) before reclassification	(50,900)	(63,620)	(40,407)	(238,689)
Amounts reclassified from accumulated other comprehensive income (loss)	423	398	1,186	786
Net current period other comprehensive (loss) income	(50,477)	(63,222)	(39,221)	(237,903)
Ending balance	(227,375)	(220,847)	(227,375)	(220,847)
Defined Benefit Pension Items
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(747)	(909)	(769)	(963)
Other comprehensive income (loss) before reclassification	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	11	27	33	81
Net current period other comprehensive (loss) income	11	27	33	81
Ending balance	$ (736)	$ (882)	$ (736)	$ (882)