ACCUMULATED OTHER COMPREHENSIVE LOSS - Summary of Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Accumulated Other Comprehensive Loss
Beginning balance	$ 2,347,952	$ 2,212,525	$ 2,304,983	$ 2,247,713
Other comprehensive income before reclassifications			32,815	16,905
Amounts reclassified from accumulated other comprehensive loss			6	7,240
Period change	34,111	60,154	32,821	24,145
Ending balance	2,412,402	2,302,373	2,412,402	2,302,373
Total
Accumulated Other Comprehensive Loss
Beginning balance	(189,975)	(211,979)	(188,685)	(175,970)
Period change	34,111	60,154	32,821	24,145
Ending balance	(155,864)	(151,825)	(155,864)	(151,825)
Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Loss
Beginning balance			(188,412)	(173,654)
Other comprehensive income before reclassifications			32,815	16,905
Amounts reclassified from accumulated other comprehensive loss			6	7,240
Period change			32,821	24,145
Ending balance	(155,591)	(149,509)	(155,591)	(149,509)
Unrealized Gains (Losses) on Defined Benefit Plans
Accumulated Other Comprehensive Loss
Beginning balance			(273)	(2,316)
Other comprehensive income before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive loss			0	0
Period change			0	0
Ending balance	$ (273)	$ (2,316)	$ (273)	$ (2,316)