ACCUMULATED OTHER COMPREHENSIVE LOSS - Accumulated Other Comprehensive Income (Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Accumulated Other Comprehensive Income (Loss)
Beginning balance	$ 2,224,803	$ 2,122,448	$ 2,247,713	$ 2,034,770
Other comprehensive income (loss) before reclassifications			(36,049)	18,834
Amounts reclassified from accumulated other comprehensive income (loss)			40	2,353
Period change	(13,950)	(19,050)	(36,009)	21,187
Ending balance	2,212,525	2,145,565	2,212,525	2,145,565
Total
Accumulated Other Comprehensive Income (Loss)
Beginning balance	(198,029)	(198,914)	(175,970)	(239,151)
Period change	(13,950)	(19,050)	(36,009)	21,187
Ending balance	(211,979)	(217,964)	(211,979)	(217,964)
Unrealized Gains (Losses) on Securities Available for Sale
Accumulated Other Comprehensive Income (Loss)
Beginning balance			(173,654)	(234,495)
Other comprehensive income (loss) before reclassifications			(36,049)	18,924
Amounts reclassified from accumulated other comprehensive income (loss)			40	2,341
Period change			(36,009)	21,265
Ending balance	(209,663)	(213,230)	(209,663)	(213,230)
Unrealized Gains (Losses) on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss)
Beginning balance			0	130
Other comprehensive income (loss) before reclassifications			0	(90)
Amounts reclassified from accumulated other comprehensive income (loss)			0	12
Period change			0	(78)
Ending balance	0	52	0	52
Unrealized Gains (Losses) on Defined Benefit Plans
Accumulated Other Comprehensive Income (Loss)
Beginning balance			(2,316)	(4,786)
Other comprehensive income (loss) before reclassifications			0	0
Amounts reclassified from accumulated other comprehensive income (loss)			0	0
Period change			0	0
Ending balance	$ (2,316)	$ (4,786)	$ (2,316)	$ (4,786)