SECURITIES (Securities available for sale) (Details) - USD ($) $ in Thousands	Mar. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale [Line Items]
Gross Unrealized Gains	$ 3,904	$ 1,495
Gross Unrealized Losses	(578,218)	(643,080)
Estimated Fair Value	1,021,283
Equity securities with a readily determinable fair value	20,604	20,314
Amortized Cost	6,670,971	6,788,729
Carried at fair value (cost of $6,670,971 at March 31, 2023, and $6,788,729 at December 31, 2022)	6,096,657	6,147,144
Total debt securities
Debt Securities, Available-for-sale [Line Items]
Total debt securities	6,650,367	6,768,415
Gross Unrealized Gains	3,904	1,495
Gross Unrealized Losses	(578,218)	(643,080)
Estimated Fair Value	6,076,053	6,126,830
U.S. treasuries
Debt Securities, Available-for-sale [Line Items]
Total debt securities	32,391	32,369
Gross Unrealized Gains	33	8
Gross Unrealized Losses	(492)	(678)
Estimated Fair Value	31,932	31,699
U.S. agencies
Debt Securities, Available-for-sale [Line Items]
Total debt securities	49,062	49,437
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(5,478)	(6,302)
Estimated Fair Value	43,584	43,135
Obligations of states and political subdivisions
Debt Securities, Available-for-sale [Line Items]
Total debt securities	1,023,650	1,049,578
Gross Unrealized Gains	47	14
Gross Unrealized Losses	(135,775)	(170,155)
Estimated Fair Value	887,922	879,437
Mortgage-backed securities - agency
Debt Securities, Available-for-sale [Line Items]
Total debt securities	2,002,260	2,042,092
Gross Unrealized Gains	85	56
Gross Unrealized Losses	(244,876)	(270,043)
Estimated Fair Value	1,757,469	1,772,105
Mortgage-backed securities - non-agency
Debt Securities, Available-for-sale [Line Items]
Total debt securities	2,260,462	2,327,308
Gross Unrealized Gains	3,739	1,417
Gross Unrealized Losses	(146,319)	(146,849)
Estimated Fair Value	2,117,882	2,181,876
Commercial mortgage-backed securities - agency
Debt Securities, Available-for-sale [Line Items]
Total debt securities	99,914	100,518
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(13,892)	(15,395)
Estimated Fair Value	86,022	85,123
Commercial mortgage-backed securities - non-agency
Debt Securities, Available-for-sale [Line Items]
Total debt securities	675,425	679,511
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(17,551)	(20,052)
Estimated Fair Value	657,874	659,459
Asset-backed securities
Debt Securities, Available-for-sale [Line Items]
Total debt securities	448,001	428,397
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(12,478)	(12,343)
Estimated Fair Value	435,523	416,054
Corporate bonds
Debt Securities, Available-for-sale [Line Items]
Total debt securities	59,202	59,205
Gross Unrealized Gains	0	0
Gross Unrealized Losses	(1,357)	(1,263)
Estimated Fair Value	$ 57,845	$ 57,942

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Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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