SECURITIES - Narrative (Details)	Sep. 30, 2023 USD ($) security	Dec. 31, 2022 USD ($) security	Oct. 31, 2022 USD ($)	Sep. 30, 2022 USD ($)
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, HTM, accumulated unrecognized loss, transferred from AFS			$ 36,800,000
Credit loss recognized	$ 0	$ 0
Accrued interest receivable	5,200,000	6,200,000
Loans held for investment	5,089,800,000	3,774,157,000		$ 3,719,000,000
Held to maturity, credit loss exposure	216,000	242,000
Amount of reserve recorded	0
Accrued interest receivable of held-to-maturity securities	2,700,000	3,600,000
Held-to-maturity, excluding accrued interest, nonaccrual	0	0
Total securities pledged	$ 1,203,000,000	$ 1,031,000,000.000
Number of securities in the portfolio that were in an unrealized loss position | security	1,318	1,265
AFS Securities
Debt and Equity Securities, FV-NI [Line Items]
Credit loss recognized	$ 0	$ 0
Obligations of U.S. government agencies and sponsored entities
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, HTM, excluding accrued interest, after allowance for credit loss, transferred from AFS			863,000
Mortgage-backed securities - commercial
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, HTM, excluding accrued interest, after allowance for credit loss, transferred from AFS			1,200,000
Tax-exempt and taxable obligations of states and municipal subdivisions
Debt and Equity Securities, FV-NI [Line Items]
Debt securities, HTM, excluding accrued interest, after allowance for credit loss, transferred from AFS			$ 137,500,000
Financial Asset, Past Due
Debt and Equity Securities, FV-NI [Line Items]
Loans held for investment	0	0
Securities held to maturity past due 30 days	$ 0	$ 0