SECURITIES AND OTHER INVESTMENTS (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) - USD ($) $ in Thousands	Dec. 31, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	$ 2,615,536	$ 3,204,361
Gross Unrealized Gains	1,592	293
Gross Unrealized (Losses)	(385,867)	(462,838)
Total AFS securities, Estimated Fair Value	2,231,261	2,741,816
U.S. government and agency securities
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	62,367	70,196
Gross Unrealized Gains	1,023	0
Gross Unrealized (Losses)	(34)	(8,253)
Total AFS securities, Estimated Fair Value	63,356	61,943
Obligations of states and political subdivisions
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	586,865	959,999
Gross Unrealized Gains	33	137
Gross Unrealized (Losses)	(111,451)	(152,701)
Total AFS securities, Estimated Fair Value	475,447	807,435
Corporate and other bonds
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	261,656	243,979
Gross Unrealized Gains	7	0
Gross Unrealized (Losses)	(19,774)	(17,599)
Total AFS securities, Estimated Fair Value	241,889	226,380
Commercial
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	300,518	349,598
Gross Unrealized Gains	274	75
Gross Unrealized (Losses)	(43,146)	(43,512)
Total AFS securities, Estimated Fair Value	257,646	306,161
Commercial | Agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	233,775	250,186
Gross Unrealized Gains	274	75
Gross Unrealized (Losses)	(41,181)	(39,268)
Total AFS securities, Estimated Fair Value	192,868	210,993
Commercial | Non-agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	66,743	99,412
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(1,965)	(4,244)
Total AFS securities, Estimated Fair Value	64,778	95,168
Residential
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	1,402,378	1,578,925
Gross Unrealized Gains	255	81
Gross Unrealized (Losses)	(211,462)	(240,773)
Total AFS securities, Estimated Fair Value	1,191,171	1,338,233
Residential | Agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	1,312,538	1,510,110
Gross Unrealized Gains	114	81
Gross Unrealized (Losses)	(205,635)	(233,961)
Total AFS securities, Estimated Fair Value	1,107,017	1,276,230
Residential | Non-agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	89,840	68,815
Gross Unrealized Gains	141	0
Gross Unrealized (Losses)	(5,827)	(6,812)
Total AFS securities, Estimated Fair Value	84,154	62,003
Other securities
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	1,752	1,664
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	0	0
Total AFS securities, Estimated Fair Value	$ 1,752	$ 1,664