ACCUMULATED OTHER COMPREHENSIVE INCOME - Changes in Accumulated Other Comprehensive Income (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	$ 562,063	$ 677,471	$ 704,906	$ 657,184
Net current period other comprehensive (loss) income	(63,195)	(11,339)	(237,822)	(16,812)
Ending balance	519,220	683,202	519,220	683,202
Total
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(158,534)	22,271	16,093	27,744
Other comprehensive income (loss) before reclassification	(63,620)	(11,385)	(238,689)	(16,318)
Amounts reclassified from accumulated other comprehensive income (loss)	425	46	867	(494)
Net current period other comprehensive (loss) income	(63,195)	(11,339)	(237,822)	(16,812)
Ending balance	(221,729)	10,932	(221,729)	10,932
Unrealized Gains and Losses on Available- for-Sales Securities
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(157,625)	23,619	17,056	29,182
Other comprehensive income (loss) before reclassification	(63,620)	(11,385)	(238,689)	(16,318)
Amounts reclassified from accumulated other comprehensive income (loss)	398	0	786	(630)
Net current period other comprehensive (loss) income	(63,222)	(11,385)	(237,903)	(16,948)
Ending balance	(220,847)	12,234	(220,847)	12,234
Defined Benefit Pension Items
AOCI Including Portion Attributable to Noncontrolling Interest, Net of Tax [Roll Forward]
Beginning balance	(909)	(1,348)	(963)	(1,438)
Other comprehensive income (loss) before reclassification	0	0	0	0
Amounts reclassified from accumulated other comprehensive income (loss)	27	46	81	136
Net current period other comprehensive (loss) income	27	46	81	136
Ending balance	$ (882)	$ (1,302)	$ (882)	$ (1,302)