SECURITIES - Summary of Amortized Cost and Fair Value of Available-For-Sale Securities and Held-To-Maturity Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2023	Dec. 31, 2022
Available-for-sale securities:
Amortized Cost	$ 1,356,696	$ 1,418,337
Gross Unrealized Gains	485	672
Gross Unrealized Losses	158,078	161,908
Securities available-for-sale	1,199,103	1,257,101
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $613,831 - 2023; $642,097 - 2022)	663,473	691,484
Gross Unrealized Gains	6,330	4,532
Gross Unrealized Losses	55,972	53,919
Estimated Fair Value	613,831	642,097
U.S. Treasury
Available-for-sale securities:
Amortized Cost	135,683	135,752
Gross Unrealized Gains	0	0
Gross Unrealized Losses	11,067	11,898
Securities available-for-sale	124,616	123,854
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $613,831 - 2023; $642,097 - 2022)	89,687	109,631
Gross Unrealized Gains	0	0
Gross Unrealized Losses	4,648	5,175
Estimated Fair Value	85,039	104,456
Obligations of U.S. government agencies and sponsored entities
Available-for-sale securities:
Amortized Cost	152,520	163,054
Gross Unrealized Gains	1	3
Gross Unrealized Losses	19,783	18,688
Securities available-for-sale	132,738	144,369
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $613,831 - 2023; $642,097 - 2022)	33,681	33,789
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2,383	2,153
Estimated Fair Value	31,298	31,636
Tax-exempt and taxable obligations of states and municipal subdivisions
Available-for-sale securities:
Amortized Cost	505,231	519,190
Gross Unrealized Gains	430	598
Gross Unrealized Losses	57,760	61,931
Securities available-for-sale	447,901	457,857
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $613,831 - 2023; $642,097 - 2022)	247,126	247,467
Gross Unrealized Gains	6,330	4,525
Gross Unrealized Losses	15,968	13,699
Estimated Fair Value	237,488	238,293
Mortgage-backed securities - residential
Available-for-sale securities:
Amortized Cost	319,417	341,272
Gross Unrealized Gains	3	11
Gross Unrealized Losses	40,622	42,041
Securities available-for-sale	278,798	299,242
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $613,831 - 2023; $642,097 - 2022)	148,859	156,119
Gross Unrealized Gains	0	0
Gross Unrealized Losses	16,902	17,479
Estimated Fair Value	131,957	138,640
Mortgage-backed securities - commercial
Available-for-sale securities:
Amortized Cost	201,601	215,200
Gross Unrealized Gains	51	60
Gross Unrealized Losses	24,471	24,363
Securities available-for-sale	177,181	190,897
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $613,831 - 2023; $642,097 - 2022)	134,120	134,478
Gross Unrealized Gains	0	7
Gross Unrealized Losses	14,016	13,798
Estimated Fair Value	120,104	120,687
Corporate obligations
Available-for-sale securities:
Amortized Cost	42,244	43,869
Gross Unrealized Gains	0	0
Gross Unrealized Losses	4,375	2,987
Securities available-for-sale	37,869	40,882
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $613,831 - 2023; $642,097 - 2022)	10,000	10,000
Gross Unrealized Gains	0	0
Gross Unrealized Losses	2,055	1,615
Estimated Fair Value	$ 7,945	$ 8,385