SECURITIES (Securities available for sale) (Details) - USD ($) $ in Thousands	Mar. 31, 2024	Dec. 31, 2023
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Gains	$ 55	$ 401
Gross Unrealized Losses	(468,137)	(453,854)
Estimated Fair Value	892,306
Equity securities with a readily determinable fair value	21,301	21,056
Amortized Cost	4,886,304	5,100,344
Estimated Fair Value	4,418,222	4,646,891
Total debt securities
Debt Securities, Available-for-sale [Line Items]
Total debt securities	4,865,003	5,079,288
Gross Unrealized Gains	55	401
Gross Unrealized Losses	(468,137)	(453,854)
Estimated Fair Value	4,396,921	4,625,835
U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Total debt securities	32,481	32,459
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(259)	(341)
Estimated Fair Value	32,222	32,118
U.S. agencies
Debt Securities, Available-for-sale [Line Items]
Total debt securities	14,084	14,724
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(192)	(194)
Estimated Fair Value	13,892	14,530
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Total debt securities	836,830	839,754
Gross Unrealized Gains	5	25
Gross Unrealized Losses	(109,344)	(98,534)
Estimated Fair Value	727,491	741,245
Mortgage-backed securities - agency
Debt Securities, Available-for-sale [Line Items]
Total debt securities	1,590,782	1,620,409
Gross Unrealized Gains	13	13
Gross Unrealized Losses	(231,254)	(226,793)
Estimated Fair Value	1,359,541	1,393,629
Mortgage-backed securities - non-agency
Debt Securities, Available-for-sale [Line Items]
Total debt securities	1,542,986	1,616,414
Gross Unrealized Gains	37	363
Gross Unrealized Losses	(85,225)	(87,649)
Estimated Fair Value	1,457,798	1,529,128
Commercial mortgage-backed securities - agency
Debt Securities, Available-for-sale [Line Items]
Total debt securities	75,782	76,076
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(11,708)	(11,288)
Estimated Fair Value	64,074	64,788
Commercial mortgage-backed securities - non-agency
Debt Securities, Available-for-sale [Line Items]
Total debt securities	436,274	526,974
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(10,180)	(12,116)
Estimated Fair Value	426,094	514,858
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Total debt securities	214,676	232,140
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(17,568)	(14,770)
Estimated Fair Value	197,108	217,370
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total debt securities	121,108	120,338
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(2,407)	(2,169)
Estimated Fair Value	$ 118,701	$ 118,169

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