CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Schedule of Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance			$ 2,205,113
Other comprehensive (loss) income	$ (128,942)	$ (202,500)	(117,542)	$ (683,420)
Less: Amounts reclassified from accumulated other comprehensive loss	4,290	5,899	12,675	5,709
Net current-period other comprehensive (loss) income	(124,652)	(196,601)	(104,867)	(677,711)
Ending balance	2,242,795		2,242,795
Amortization of unrealized losses on securities reclassified to held-to-maturity, tax expense	(1,379)	(1,884)	(4,080)	35,955
Fannie Mae (FNMA) mortgage-backed securities (MBS)
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Amortization of unrealized losses on securities reclassified to held-to-maturity, tax expense				119,800
Total
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(656,059)	(518,878)	(675,844)	(37,768)
Ending balance	(780,711)	(715,479)	(780,711)	(715,479)
Net change in investment securities available-for-sale
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(550,890)	(395,213)	(563,533)	(33,873)
Other comprehensive (loss) income	(127,523)	(202,520)	(114,880)	(563,860)
Less: Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net current-period other comprehensive (loss) income	(127,523)	(202,520)	(114,880)	(563,860)
Ending balance	(678,413)	(597,733)	(678,413)	(597,733)
Net change in investment securities held-to-maturity
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(99,945)	(119,649)	(108,503)	175
Other comprehensive (loss) income	0	(1)	0	(119,769)
Less: Amounts reclassified from accumulated other comprehensive loss	4,366	5,967	12,924	5,911
Net current-period other comprehensive (loss) income	4,366	5,966	12,924	(113,858)
Ending balance	(95,579)	(113,683)	(95,579)	(113,683)
Net change in defined benefit plan
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(4,571)	(4,746)	(4,482)	(4,691)
Other comprehensive (loss) income	(3)	(4)	2	(4)
Less: Amounts reclassified from accumulated other comprehensive loss	(48)	(27)	(142)	(82)
Net current-period other comprehensive (loss) income	(51)	(31)	(140)	(86)
Ending balance	(4,622)	(4,777)	(4,622)	(4,777)
Net change in fair value of derivatives used for cash flow hedges
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	(1,115)	189	108	268
Other comprehensive (loss) income	(1,608)	0	(2,752)	0
Less: Amounts reclassified from accumulated other comprehensive loss	(28)	(41)	(107)	(120)
Net current-period other comprehensive (loss) income	(1,636)	(41)	(2,859)	(120)
Ending balance	(2,751)	148	(2,751)	148
Net change in equity method investments
AOCI Attributable to Parent, Net of Tax [Roll Forward]
Beginning balance	462	541	566	353
Other comprehensive (loss) income	192	25	88	213
Less: Amounts reclassified from accumulated other comprehensive loss	0	0	0	0
Net current-period other comprehensive (loss) income	192	25	88	213
Ending balance	$ 654	$ 566	$ 654	$ 566