CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	$ 2,477,636
Other comprehensive (loss) income	(46,536)	$ 53,350
Less: Amounts reclassified from accumulated other comprehensive loss	3,620	4,079
Net current-period other comprehensive (loss) income	(42,916)	57,429
Ending balance	2,473,481
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(593,991)	(675,844)
Ending balance	(636,907)	(618,415)
Net change in investment securities available-for-sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(499,932)	(563,533)
Other comprehensive (loss) income	(40,007)	53,010
Less: Amounts reclassified from accumulated other comprehensive loss	0	0
Net current-period other comprehensive (loss) income	(40,007)	53,010
Ending balance	(539,939)	(510,523)
Net change in investment securities held-to-maturity
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(91,523)	(108,503)
Other comprehensive (loss) income	0	(1)
Less: Amounts reclassified from accumulated other comprehensive loss	3,669	4,166
Net current-period other comprehensive (loss) income	3,669	4,165
Ending balance	(87,854)	(104,338)
Net change in defined benefit plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,614)	(4,482)
Other comprehensive (loss) income	(75)	12
Less: Amounts reclassified from accumulated other comprehensive loss	(49)	(47)
Net current-period other comprehensive (loss) income	(124)	(35)
Ending balance	(4,738)	(4,517)
Net change in fair value of derivatives used for cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	1,597	108
Other comprehensive (loss) income	(6,433)	332
Less: Amounts reclassified from accumulated other comprehensive loss	0	(40)
Net current-period other comprehensive (loss) income	(6,433)	292
Ending balance	(4,836)	400
Net change in equity method investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	481	566
Other comprehensive (loss) income	(21)	(3)
Less: Amounts reclassified from accumulated other comprehensive loss	0	0
Net current-period other comprehensive (loss) income	(21)	(3)
Ending balance	$ 460	$ 563