Borrowings - Additional information (Details) $ in Thousands			1 Months Ended	3 Months Ended		9 Months Ended
	Feb. 24, 2023 USD ($)	Feb. 24, 2020 USD ($)	Dec. 31, 2016	Jun. 30, 2023 USD ($)	Jun. 30, 2021 USD ($)	Sep. 30, 2024 USD ($) item	Sep. 30, 2023 USD ($)	Dec. 31, 2023 USD ($)
Borrowings
Number of customers having secured balances exceeding specified percentage of stockholders equity | item						0
Threshold percentage of stockholders' equity						10.00%
Borrowings at FHLBC as percentage of total assets						35.00%
FHLBC stock						$ 15,300		$ 18,500
Proceeds from term note		$ 30,000
Repayment of term note							$ 9,000
Basis points added to reference rate (as a percent)		1.75%
Outstanding, net of deferred issuance costs						59,400		59,400
Asset Pledged as Collateral with Right | Securities sold under repurchase agreements
Borrowings
Investment securities pledged with financial institutions, dollars						75,000		45,700
Securities sold under repurchase agreements
Borrowings
Investment securities pledged with financial institutions, dollars						$ 53,900		26,500
Federal Home Loan Bank Advances
Borrowings
Borrowings at FHLBC as percentage of book value of certain mortgage loans						60.00%
FHLBC advance amount						$ 335,000		$ 405,000
FHLBC stock						15,300
Principal balance of loans collateralized						1,400,000
Combined collateral value						953,000,000
Amount available for additional borrowings						$ 653,000
Senior notes
Borrowings
Interest rate (as a percent)			5.75%
Debt Instrument, Term			10 years
Interest rate term			5 years
Effective interest rate							9.39%
Debt issuance costs				$ 362
Debt instrument redemption price, percentage				12.85%		100.00%
Debt redeemed amount				$ 45,000
Senior notes | Debt Instrument Variable Rate Base LIBOR
Borrowings
Basis points added to reference rate (as a percent)			3.85%
Term Debt
Borrowings
Proceeds from term note		$ 20,000
Repayment of term note	$ 9,000
Debt term		3 years
Subordinated Notes Due 2031
Borrowings
Interest rate (as a percent)					3.50%
Face amount					$ 60,000
Subordinated Notes Due 2031 | Three Months Secured Overnight Financing Rate
Borrowings
Basis points added to reference rate (as a percent)					2.73%