SECURITIES - Summary of Amortized Cost and Fair Value of Available-For-Sale Securities and Held-To-Maturity Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2022	Dec. 31, 2021
Available-for-sale securities:
Amortized Cost	$ 1,638,341	$ 1,741,153
Gross Unrealized Gains	1,413	21,775
Gross Unrealized Losses	150,507	11,096
Securities available-for-sale:	1,489,247	1,751,832
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $561,333 - 2022; $0 - 2021)	593,154	0
Gross Unrealized Gains	228
Gross Unrealized Losses	32,049
Estimated Fair Value	561,333	0
U.S. Treasury
Available-for-sale securities:
Amortized Cost	135,820	135,889
Gross Unrealized Gains	0	83
Gross Unrealized Losses	8,979	814
Securities available-for-sale:	126,841	135,158
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $561,333 - 2022; $0 - 2021)	109,527
Gross Unrealized Gains	0
Gross Unrealized Losses	3,403
Estimated Fair Value	106,124
Obligations of U.S. government agencies and sponsored entities
Available-for-sale securities:
Amortized Cost	172,020	182,877
Gross Unrealized Gains	16	1,238
Gross Unrealized Losses	13,375	1,094
Securities available-for-sale:	158,660	183,021
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $561,333 - 2022; $0 - 2021)	33,127
Gross Unrealized Gains	0
Gross Unrealized Losses	489
Estimated Fair Value	32,638
Tax-exempt and taxable obligations of states and municipal subdivisions
Available-for-sale securities:
Amortized Cost	671,353	698,861
Gross Unrealized Gains	1,126	12,452
Gross Unrealized Losses	80,661	2,811
Securities available-for-sale:	591,818	708,502
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $561,333 - 2022; $0 - 2021)	146,958
Gross Unrealized Gains	162
Gross Unrealized Losses	11,576
Estimated Fair Value	135,544
Mortgage-backed securities - residential
Available-for-sale securities:
Amortized Cost	368,957	410,269
Gross Unrealized Gains	71	4,123
Gross Unrealized Losses	29,201	3,425
Securities available-for-sale:	339,827	410,967
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $561,333 - 2022; $0 - 2021)	163,453
Gross Unrealized Gains	0
Gross Unrealized Losses	10,139
Estimated Fair Value	153,314
Mortgage-backed securities - commercial
Available-for-sale securities:
Amortized Cost	251,865	277,353
Gross Unrealized Gains	118	2,917
Gross Unrealized Losses	17,176	2,939
Securities available-for-sale:	234,807	277,331
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $561,333 - 2022; $0 - 2021)	130,089
Gross Unrealized Gains	66
Gross Unrealized Losses	5,793
Estimated Fair Value	124,362
Corporate obligations
Available-for-sale securities:
Amortized Cost	38,326	35,904
Gross Unrealized Gains	83	962
Gross Unrealized Losses	1,115	13
Securities available-for-sale:	37,294	$ 36,853
Held-to-maturity:
Securities held to maturity, net of allowance for credit losses of $0 (fair value: $561,333 - 2022; $0 - 2021)	10,000
Gross Unrealized Gains	0
Gross Unrealized Losses	649
Estimated Fair Value	$ 9,351

Amount, before tax, of unrealized gain in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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Amount, before tax, of unrealized loss in accumulated other comprehensive income (AOCI) on investment in debt security measured at fair value with change in fair value recognized in other comprehensive income (available-for-sale).

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