ACCUMULATED OTHER COMPREHENSIVE INCOME (LOSS) - Accumulated Other Comprehensive income (loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Accumulated other comprehensive income (loss), net of tax:
Balance	$ 1,396,517	$ 1,226,225
Net other comprehensive income (loss) during the period	5,973	6,113
Balance	1,412,013	1,239,371
Total Accumulated Other Comprehensive Income (Loss)
Accumulated other comprehensive income (loss), net of tax:
Balance	(45,018)	(91,579)
Other comprehensive income (loss) before reclassifications	4,256	4,178
Amounts reclassified from accumulated other comprehensive income (loss)	1,717	1,935
Net other comprehensive income (loss) during the period	5,973	6,113
Balance	(39,045)	(85,466)
Securities
Accumulated other comprehensive income (loss), net of tax:
Balance	(43,767)	(90,242)
Other comprehensive income (loss) before reclassifications	6,136	2,360
Amounts reclassified from accumulated other comprehensive income (loss)	502	490
Net other comprehensive income (loss) during the period	6,638	2,850
Balance	(37,129)	(87,392)
Defined Benefit Plans
Accumulated other comprehensive income (loss), net of tax:
Balance	(7,499)	(6,430)
Other comprehensive income (loss) before reclassifications	3,364	361
Amounts reclassified from accumulated other comprehensive income (loss)	(60)	(216)
Net other comprehensive income (loss) during the period	3,304	145
Balance	(4,195)	(6,285)
Derivatives
Accumulated other comprehensive income (loss), net of tax:
Balance	6,248	5,093
Other comprehensive income (loss) before reclassifications	(5,244)	1,457
Amounts reclassified from accumulated other comprehensive income (loss)	1,275	1,661
Net other comprehensive income (loss) during the period	(3,969)	3,118
Balance	$ 2,279	$ 8,211