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	Jun. 30, 2024 USD ($) security	Dec. 31, 2023 USD ($) security
Fair Value
Less than 12 Months	$ 107,497	$ 67,007
12 Months or Longer	1,475,469	1,493,547
Total	1,582,966	1,560,554
Gross Unrealized Losses
Less than 12 Months	3,803	1,101
12 Months or Longer	261,920	219,453
Total	$ 265,723	$ 220,554
Number of Securities | security	910	865
U.S. Government-sponsored agency securities
Fair Value
Less than 12 Months	$ 0	$ 0
12 Months or Longer	91,277	95,307
Total	91,277	95,307
Gross Unrealized Losses
Less than 12 Months	0	0
12 Months or Longer	17,565	16,214
Total	$ 17,565	$ 16,214
Number of Securities | security	14	14
State and municipal
Fair Value
Less than 12 Months	$ 50,145	$ 55,514
12 Months or Longer	973,117	963,584
Total	1,023,262	1,019,098
Gross Unrealized Losses
Less than 12 Months	2,900	1,076
12 Months or Longer	150,582	115,146
Total	$ 153,482	$ 116,222
Number of Securities | security	725	691
U.S. Government-sponsored mortgage-backed securities
Fair Value
Less than 12 Months	$ 57,352	$ 11,493
12 Months or Longer	399,051	422,868
Total	456,403	434,361
Gross Unrealized Losses
Less than 12 Months	903	25
12 Months or Longer	92,874	86,965
Total	$ 93,777	$ 86,990
Number of Securities | security	161	150
Corporate obligations
Fair Value
Less than 12 Months	$ 0	$ 0
12 Months or Longer	12,024	11,788
Total	12,024	11,788
Gross Unrealized Losses
Less than 12 Months	0	0
12 Months or Longer	899	1,128
Total	$ 899	$ 1,128
Number of Securities | security	10	10