ACCUMULATED OTHER COMPREHENSIVE LOSS - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Accumulated Other Comprehensive Loss
Beginning balance	$ 2,304,983	$ 2,247,713
Other comprehensive loss before reclassifications	(1,632)	(22,061)
Amounts reclassified from accumulated other comprehensive loss	6	2
Period change	(1,626)	(22,059)
Ending balance	2,332,214	2,224,803
Total
Accumulated Other Comprehensive Loss
Beginning balance	(188,685)	(175,970)
Period change	(1,626)	(22,059)
Ending balance	(190,311)	(198,029)
Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Loss
Beginning balance	(188,412)	(173,654)
Other comprehensive loss before reclassifications	(1,632)	(22,061)
Amounts reclassified from accumulated other comprehensive loss	6	2
Period change	(1,626)	(22,059)
Ending balance	(190,038)	(195,713)
Unrealized Gains (Losses) on Defined Benefit Plans
Accumulated Other Comprehensive Loss
Beginning balance	(273)	(2,316)
Other comprehensive loss before reclassifications	0	0
Amounts reclassified from accumulated other comprehensive loss	0	0
Period change	0	0
Ending balance	$ (273)	$ (2,316)