CHANGE IN ACCUMULATED OTHER COMPREHENSIVE LOSS - Components of Accumulated Other Comprehensive Loss (Details) - USD ($) $ in Thousands	1 Months Ended	12 Months Ended
	Jun. 30, 2022	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		$ 2,477,636
Other comprehensive income (loss) before reclassifications		(45,812)	$ 65,244	$ (648,898)
Less: Amounts reclassified from accumulated other comprehensive income (loss)		14,926	16,609	10,822
Total other comprehensive (loss) income		(30,886)	81,853	(638,076)
Ending balance		2,589,752	2,477,636
Amortization of unrealized gain on securities reclassified to held-to-maturity, tax expense		(4,774)	(5,361)	(34,319)
Fannie Mae (FNMA) mortgage-backed securities (MBS)
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Amortization of unrealized gain on securities reclassified to held-to-maturity, tax expense	$ 119,800
Total
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(593,991)	(675,844)	(37,768)
Total other comprehensive (loss) income		(30,886)	81,853	(638,076)
Ending balance		(624,877)	(593,991)	(675,844)
Net change in investment securities available for sale
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(499,932)	(563,533)	(33,873)
Other comprehensive income (loss) before reclassifications		(37,857)	63,601	(529,660)
Less: Amounts reclassified from accumulated other comprehensive income (loss)		0	0	0
Total other comprehensive (loss) income		(37,857)	63,601	(529,660)
Ending balance		(537,789)	(499,932)	(563,533)
Net change in investment securities held to maturity
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(91,523)	(108,503)	175
Other comprehensive income (loss) before reclassifications		0	0	(119,769)
Less: Amounts reclassified from accumulated other comprehensive income (loss)		15,118	16,980	11,091
Total other comprehensive (loss) income		15,118	16,980	(108,678)
Ending balance		(76,405)	(91,523)	(108,503)
Net change in defined benefit plan
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		(4,614)	(4,482)	(4,691)
Other comprehensive income (loss) before reclassifications		991	132	318
Less: Amounts reclassified from accumulated other comprehensive income (loss)		(192)	(264)	(109)
Total other comprehensive (loss) income		799	(132)	209
Ending balance		(3,815)	(4,614)	(4,482)
Net change in fair value of derivatives used for cash flow hedges
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		1,597	108	268
Other comprehensive income (loss) before reclassifications		(8,894)	1,596	0
Less: Amounts reclassified from accumulated other comprehensive income (loss)		0	(107)	(160)
Total other comprehensive (loss) income		(8,894)	1,489	(160)
Ending balance		(7,297)	1,597	108
Net change in equity method investments
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Beginning balance		481	566	353
Other comprehensive income (loss) before reclassifications		(52)	(85)	213
Less: Amounts reclassified from accumulated other comprehensive income (loss)		0	0	0
Total other comprehensive (loss) income		(52)	(85)	213
Ending balance		$ 429	$ 481	$ 566