Subordinated Notes and Junior Subordinated Debentures - Additional Information (Details) - USD ($)		3 Months Ended		6 Months Ended	9 Months Ended		12 Months Ended
	Jun. 26, 2020	Sep. 30, 2020	Sep. 30, 2019	Jun. 30, 2020	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019	Aug. 03, 2020
Debt Instrument [Line Items]
Principal amount		$ 45,000,000			$ 45,000,000		$ 46,500,000
Other non-interest expense		3,959,000	$ 4,224,000		$ 12,310,000	$ 12,657,000
6.00 % Fixed-To-Floating Subordinate Notes Mature on July 1, 2030 | Subordinated Notes
Debt Instrument [Line Items]
Debt instrument, face amount	$ 50,000,000.0							$ 25,000,000.0
Debt instrument, interest rate	6.00%
Debt instrument, maturity date	Jul. 01, 2030
Debt instrument, redemption, description					As of September 30, 2020, the net liability outstanding of the subordinated notes was $73.3 million The Company may, at its option, redeem the notes, in whole or in part, on a semi-annual basis beginning on July 1, 2025, subject to obtaining the prior approval of the Federal Reserve to the extent such approval is then required.
Debt issuance costs	$ 1,700,000
Debt issuance costs, amortization period	10 years
Net liability outstanding of subordinated notes		73,300,000			$ 73,300,000
6.00 % Fixed-To-Floating Subordinate Notes Mature on July 1, 2030 | Subordinated Notes | Three-Month Secured Overnight Financing Rate Plus 588 Basis Points
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis					The subordinated notes bear a fixed interest rate of 6.00% until July 1, 2025 and a floating interest rate equal to a benchmark rate, which is expected to be three-month Secured Overnight Financing Rate plus 588 basis points thereafter until maturity.
Metropolitan Statutory Trust 1
Debt Instrument [Line Items]
Principal amount		$ 35,000,000			$ 35,000,000		$ 35,000,000
Metropolitan Statutory Trust 1 | Junior Subordinated Debentures
Debt Instrument [Line Items]
Debt instrument, maturity date					Mar. 17, 2034
Contractual rate		3.03%			3.03%		4.69%
Accrued interest payable		$ 43,000			$ 43,000		$ 71,000
Metropolitan Statutory Trust 1 | Junior Subordinated Debentures | Three-month LIBOR
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis					Three-month LIBOR + 2.79%
Interest rate spread					2.79%		2.79%
RidgeStone Capital Trust I
Debt Instrument [Line Items]
Principal amount							$ 1,500,000
RidgeStone Capital Trust I | Junior Subordinated Debentures
Debt Instrument [Line Items]
Debt instrument, maturity date					Jun. 30, 2033
Contractual rate							6.38%
Accrued interest payable							$ 0
Redemption of debentures in whole at par value				$ 1,500,000
Other non-interest expense				$ 112,000
RidgeStone Capital Trust I | Junior Subordinated Debentures | Five-year LIBOR
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis					Five-year LIBOR + 3.50%
Interest rate spread					3.50%		3.50%
First Evanston Bancorp Trust I
Debt Instrument [Line Items]
Principal amount		$ 10,000,000			$ 10,000,000		$ 10,000,000
First Evanston Bancorp Trust I | Junior Subordinated Debentures
Debt Instrument [Line Items]
Debt instrument, maturity date					Mar. 15, 2035
Contractual rate		2.03%			2.03%		3.67%
Accrued interest payable		$ 9,000			$ 9,000		$ 17,000
First Evanston Bancorp Trust I | Junior Subordinated Debentures | Three-month LIBOR
Debt Instrument [Line Items]
Debt instrument, description of variable rate basis					Three-month LIBOR + 1.78%
Interest rate spread					1.78%		1.78%