SECURITIES (Amortized Cost, Gross Unrealized Gains and Losses, and Estimated Fair Values of Investment Securities) (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	$ 2,632,554	$ 3,204,361
Gross Unrealized Gains	65	293
Gross Unrealized (Losses)	(450,172)	(462,838)
Total AFS securities, Estimated Fair Value	2,182,448	2,741,816
U.S. government and agency securities
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	69,359	70,196
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(8,012)	(8,253)
Total AFS securities, Estimated Fair Value	61,347	61,943
Obligations of states and political subdivisions
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	649,572	959,999
Gross Unrealized Gains	2	137
Gross Unrealized (Losses)	(136,548)	(152,701)
Total AFS securities, Estimated Fair Value	513,026	807,435
Corporate and other bonds
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	169,995	243,979
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(27,423)	(17,599)
Total AFS securities, Estimated Fair Value	142,572	226,380
Commercial
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	307,549	349,598
Gross Unrealized Gains	59	75
Gross Unrealized (Losses)	(45,653)	(43,512)
Total AFS securities, Estimated Fair Value	261,955	306,161
Commercial | Agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	229,165	250,186
Gross Unrealized Gains	59	75
Gross Unrealized (Losses)	(43,030)	(39,268)
Total AFS securities, Estimated Fair Value	186,194	210,993
Commercial | Non-agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	78,384	99,412
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(2,623)	(4,244)
Total AFS securities, Estimated Fair Value	75,761	95,168
Residential
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	1,434,376	1,578,925
Gross Unrealized Gains	4	81
Gross Unrealized (Losses)	(232,535)	(240,773)
Total AFS securities, Estimated Fair Value	1,201,845	1,338,233
Residential | Agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	1,363,949	1,510,110
Gross Unrealized Gains	4	81
Gross Unrealized (Losses)	(226,232)	(233,961)
Total AFS securities, Estimated Fair Value	1,137,721	1,276,230
Residential | Non-agency
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	70,427	68,815
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	(6,303)	(6,812)
Total AFS securities, Estimated Fair Value	64,124	62,003
Other securities
Debt Securities, Available-for-sale Securities, Amortized Cost Basis [Abstract]
Total AFS securities	1,703	1,664
Gross Unrealized Gains	0	0
Gross Unrealized (Losses)	0	0
Total AFS securities, Estimated Fair Value	$ 1,703	$ 1,664