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	Sep. 30, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Fair Value
Less than 12 Months	$ 59,052	$ 67,007
12 Months or Longer	1,378,921	1,493,547
Total	1,437,973	1,560,554
Gross Unrealized Losses
Less than 12 Months	1,412	1,101
12 Months or Longer	190,313	219,453
Total	$ 191,725	$ 220,554
Number of Securities | security	793	865
U.S. Government-sponsored agency securities
Fair Value
Less than 12 Months	$ 0	$ 0
12 Months or Longer	85,033	95,307
Total	85,033	95,307
Gross Unrealized Losses
Less than 12 Months	0	0
12 Months or Longer	12,637	16,214
Total	$ 12,637	$ 16,214
Number of Securities | security	13	14
State and municipal
Fair Value
Less than 12 Months	$ 40,136	$ 55,514
12 Months or Longer	934,947	963,584
Total	975,083	1,019,098
Gross Unrealized Losses
Less than 12 Months	1,335	1,076
12 Months or Longer	105,602	115,146
Total	$ 106,937	$ 116,222
Number of Securities | security	662	691
U.S. Government-sponsored mortgage-backed securities
Fair Value
Less than 12 Months	$ 18,916	$ 11,493
12 Months or Longer	346,666	422,868
Total	365,582	434,361
Gross Unrealized Losses
Less than 12 Months	77	25
12 Months or Longer	71,423	86,965
Total	$ 71,500	$ 86,990
Number of Securities | security	108	150
Corporate obligations
Fair Value
Less than 12 Months	$ 0	$ 0
12 Months or Longer	12,275	11,788
Total	12,275	11,788
Gross Unrealized Losses
Less than 12 Months	0	0
12 Months or Longer	651	1,128
Total	$ 651	$ 1,128
Number of Securities | security	10	10