SECURITIES - Summary of Available For Sale Securities (Details) - USD ($)	Mar. 31, 2022	Dec. 31, 2021
Information related to available for sale securities
Amortized Cost	$ 1,639,941,000	$ 1,376,969,000
Gross Unrealized Gain	5,288,000	30,244,000
Gross Unrealized Losses	(122,694,000)	(8,655,000)
Allowance for Credit Losses	0	0
Fair Value	1,522,535,000	1,398,558,000
U.S. Treasury securities
Information related to available for sale securities
Amortized Cost	2,250,000	900,000
Gross Unrealized Gain	0	0
Gross Unrealized Losses	(4,000)	0
Allowance for Credit Losses	0	0
Fair Value	2,246,000	900,000
U.S. government sponsored agencies
Information related to available for sale securities
Amortized Cost	164,514,000	145,858,000
Gross Unrealized Gain	0	39,000
Gross Unrealized Losses	(11,622,000)	(2,445,000)
Allowance for Credit Losses	0	0
Fair Value	152,892,000	143,452,000
Mortgage-backed securities: residential
Information related to available for sale securities
Amortized Cost	634,654,000	487,157,000
Gross Unrealized Gain	680,000	4,455,000
Gross Unrealized Losses	(39,013,000)	(4,936,000)
Allowance for Credit Losses	0	0
Fair Value	596,321,000	486,676,000
Mortgage-backed securities: commercial
Information related to available for sale securities
Amortized Cost	96,000	522,000
Gross Unrealized Gain	0	1,000
Gross Unrealized Losses	0	0
Allowance for Credit Losses	0	0
Fair Value	96,000	523,000
State and municipal securities
Information related to available for sale securities
Amortized Cost	838,427,000	742,532,000
Gross Unrealized Gain	4,608,000	25,749,000
Gross Unrealized Losses	(72,055,000)	(1,274,000)
Allowance for Credit Losses	0	0
Fair Value	$ 770,980,000	$ 767,007,000

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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Amount excluding accrued interest, of allowance for credit loss 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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