INVESTMENT SECURITIES - Investments' Gross Unrealized Losses and Fair Value Aggregated by Investment Category and Length of Time in Continuous Unrealized Loss Position (Details) $ in Thousands	Mar. 31, 2023 USD ($) security	Dec. 31, 2022 USD ($) security
Fair Value
Less than 12 Months	$ 392,852	$ 1,423,379
12 Months or Longer	1,330,087	487,129
Total	1,722,939	1,910,508
Gross Unrealized Losses
Less than 12 Months	19,355	172,828
12 Months or Longer	226,931	124,297
Total	$ 246,286	$ 297,125
Number of Securities | security	966	1,154
U.S. Treasury
Fair Value
Less than 12 Months	$ 737	$ 2,459
12 Months or Longer	957	0
Total	1,694	2,459
Gross Unrealized Losses
Less than 12 Months	8	42
12 Months or Longer	24	0
Total	$ 32	$ 42
Number of Securities | security	3	5
U.S. Government-sponsored agency securities
Fair Value
Less than 12 Months	$ 36,595	$ 48,940
12 Months or Longer	65,197	53,022
Total	101,792	101,962
Gross Unrealized Losses
Less than 12 Months	2,204	4,973
12 Months or Longer	12,949	12,219
Total	$ 15,153	$ 17,192
Number of Securities | security	15	16
State and municipal
Fair Value
Less than 12 Months	$ 290,254	$ 1,177,104
12 Months or Longer	823,441	108,652
Total	1,113,695	1,285,756
Gross Unrealized Losses
Less than 12 Months	13,634	150,096
12 Months or Longer	125,692	28,630
Total	$ 139,326	$ 178,726
Number of Securities | security	765	946
U.S. Government-sponsored mortgage-backed securities
Fair Value
Less than 12 Months	$ 54,013	$ 182,700
12 Months or Longer	439,588	325,455
Total	493,601	508,155
Gross Unrealized Losses
Less than 12 Months	2,801	16,910
12 Months or Longer	88,170	83,448
Total	$ 90,971	$ 100,358
Number of Securities | security	173	177
Corporate obligations
Fair Value
Less than 12 Months	$ 11,253	$ 12,176
12 Months or Longer	904	0
Total	12,157	12,176
Gross Unrealized Losses
Less than 12 Months	708	807
12 Months or Longer	96	0
Total	$ 804	$ 807
Number of Securities | security	10	10