INVESTMENTS - Summary of Held-To-Maturity and Available-For-Sale Investment Securities (Details) - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022
Investment Holdings [Line Items]
Total	$ 81,236	$ 84,021
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	17	105
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(11,408)	(7,641)
Held-to-Maturity Market Value	69,845	76,485
Total	3,526,096	3,827,418
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	472	834
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(482,207)	(418,604)
Investment securities available-for-sale	3,044,361	3,409,648
U.S. Treasuries
Investment Holdings [Line Items]
Total	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held-to-Maturity Market Value	0	0
Total	37,085	37,312
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(4,943)	(4,616)
Investment securities available-for-sale	32,142	32,696
Securities of U.S. government agencies and corporations
Investment Holdings [Line Items]
Total	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held-to-Maturity Market Value	0	0
Total	81,434	80,382
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(15,309)	(13,914)
Investment securities available-for-sale	66,125	66,468
Residential Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held-to-Maturity Market Value	0	0
Total	705,681	747,478
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	47
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(121,198)	(97,462)
Investment securities available-for-sale	584,483	650,063
Commercial Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	33,399	35,363
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(5,958)	(4,114)
Held-to-Maturity Market Value	27,441	31,249
Total	599,969	676,934
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	2
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(50,399)	(47,374)
Investment securities available-for-sale	549,570	629,562
Collateralized Mortgage Backed Securities [Member]
Investment Holdings [Line Items]
Total	8,410	9,280
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(1,182)	(827)
Held-to-Maturity Market Value	7,228	8,453
Total	488,590	538,970
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	181
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(75,659)	(61,439)
Investment securities available-for-sale	412,931	477,712
Obligations of state and other political subdivisions
Investment Holdings [Line Items]
Total	8,177	8,128
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	17	105
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(530)	(201)
Held-to-Maturity Market Value	7,664	8,032
Total	814,669	832,066
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	472	565
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(151,398)	(124,168)
Investment securities available-for-sale	663,743	708,463
Asset-backed Securities [Member]
Investment Holdings [Line Items]
Total	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	0	0
Held-to-Maturity Market Value	0	0
Total	661,779	772,261
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	39
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(49,679)	(60,975)
Investment securities available-for-sale	612,100	711,325
Other securities
Investment Holdings [Line Items]
Total	31,250	31,250
Debt Securities, Held-to-maturity, Accumulated Unrecognized Gain	0	0
Debt Securities, Held-to-maturity, Accumulated Unrecognized Loss	(3,738)	(2,499)
Held-to-Maturity Market Value	27,512	28,751
Total	136,889	142,015
Available for Sale Securities Gross Unrealized Gain Accumulated In Investments	0	0
Available for Sale Securities Gross Unrealized Loss Accumulated In Investments	(13,622)	(8,656)
Investment securities available-for-sale	$ 123,267	$ 133,359