SECURITIES - Narrative (Details) - USD ($)	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Securities available-for-sale:
Transfer from securities held-to-maturity	$ 0		$ 0	$ 400,000,000.0
Securities available-for-sale transferred to held-to-maturity				372,154,000
Unrealized loss on transfer of securities to held to maturity				(27,800,000)
Gain (loss) on transfer of securities to held-to-maturity				0
Transfers to or from securities held-to-maturity		$ 0		0
Securities held-to-maturity	$ 495,986,000		$ 495,986,000		$ 505,759,000
Number of holdings of securities of any one issuer in an amount greater than 10% of stockholders equity	0		0		0
Threshold for disclosure percentage			10.00%		10.00%
Available for sale debt securities, unrealized loss position due to credit	$ 0		$ 0
Allowance for credit losses on available for sale debt securities	0		0
Accrued interest receivable on securities			3,300,000		$ 5,400,000
Unrealized losses are related to credit losses	0		0
Securities pledged
Securities available-for-sale:
Carrying amount of securities pledged	$ 470,000,000.0		$ 470,000,000.0		$ 631,400,000
Financial Instrument, Owned, Pledged Status [Extensible Enumeration]	Securities pledged		Securities pledged		Securities pledged
Carrying Amount
Securities available-for-sale:
Securities held-to-maturity	$ 600,291,000		$ 600,291,000		$ 585,798,000
Fair Value
Securities available-for-sale:
Securities available-for-sale transferred to held-to-maturity				$ 372,200,000
Securities held-to-maturity	$ 495,986,000		$ 495,986,000		$ 505,759,000