INVESTMENT SECURITIES - Narrative (Details)	3 Months Ended	6 Months Ended	9 Months Ended		12 Months Ended
	Mar. 31, 2025 USD ($)	Jun. 30, 2023 fund	Sep. 30, 2025 USD ($)	Sep. 30, 2024 USD ($)	Dec. 31, 2024 USD ($)	Dec. 31, 2022 USD ($)
Debt Securities, Available-for-sale [Line Items]
Number of bank technology funds | fund		2
Debt securities pledged as collateral			$ 30,200,000		$ 34,900,000
Shareholder equity held by one issuer (as a percent)			10.00%		10.00%
Proceeds from sale of debt securities			$ 0	$ 0
AFS, accrued interest receivable			100,000
HTM, accrued interest receivable			500,000		$ 300,000
Held-to-maturity debt securities, allowance for credit losses			71,000		71,000
Bank Technology Fund
Debt Securities, Available-for-sale [Line Items]
Contractual obligation						$ 6,000,000
Return of capital, received	$ 300,000		100,000
Balance with SBIC included in other assets			4,300,000		2,500,000
Committed investments to be made in the future			4,700,000
Bank Technology Fund | Other Assets
Debt Securities, Available-for-sale [Line Items]
Contribution to committed investments			1,800,000		500,000
Sale Leaseback Fund
Debt Securities, Available-for-sale [Line Items]
Contractual obligation			3,000,000
Small Business Investment Company ("SBIC")
Debt Securities, Available-for-sale [Line Items]
Contractual obligation			600,000
Small Business Investment Company ("SBIC") | Other Assets
Debt Securities, Available-for-sale [Line Items]
Contribution to committed investments			0		$ 200,000
Balance with SBIC included in other assets			$ 2,400,000