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Borrowings - Additional information (Details) |  |  | 3 Months Ended |  |
--- | --- | --- | --- | --- | ---
Apr. 06, 2021 USD ($) | Feb. 24, 2020 USD ($) | Mar. 31, 2022 USD ($) item | Dec. 31, 2016 | Dec. 31, 2021 USD ($) | Apr. 20, 2018 USD ($)
Borrowings |  |  |  |  |  |
Threshold percentage of stockholders' equity |  |  | 10.00% |  |  |
Borrowings at FHLBC as percentage of total assets |  |  | 35.00% |  |  |
Borrowings at FHLBC as percentage of book value of certain mortgage loans |  |  | 60.00% |  |  |
FHLBC stock |  |  | $ 7,100,000 |  | $ 7,100,000 |
Federal Home Loan Bank Chicago ("FHLBC") and Federal Reserve Bank Chicago ("FRBC") stock |  |  | 21,974,000 |  | 13,257,000 |
Proceeds from term note |  | $ 30,000,000.0 |  |  |  |
Senior notes |  |  | 44,506,000 |  | 44,480,000 |
Basis points added to reference rate (as a percent) |  | 175.00% |  |  |  |
Total borrowings |  |  | 181,025,000 |  | 198,876,000 |
GCFC/ABC Bank |  |  |  |  |  |
Borrowings |  |  |  |  |  |
FHLBC advance amount |  |  | $ 6,000,000.0 |  |  |
Debt assumed |  |  |  |  |  | $ 23,400,000
GCFC/ABC Bank | Maximum |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Interest rate (as a percent) |  |  | 2.83% |  |  |
Three Months Secured Overnight Financing Rate |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Basis points added to reference rate (as a percent) | 273.00% |  |  |  |  |
Securities sold under repurchase agreements |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Carrying amount of securities secured |  |  | $ 33,500,000 |  | 50,300,000 |
Fair value of the pledged collateral |  |  | $ 107,300,000 |  | 113,000,000.0 |
Number of customers having secured balances exceeding specified percentage of stockholders equity | item |  |  | 0 |  |  |
Total borrowings |  |  | $ 33,521,000 |  | 50,337,000 |
Federal Home Loan Bank Advances |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Borrowings at FHLBC as percentage of book value of certain mortgage loans |  |  | 60.00% |  |  |
FHLBC advance amount |  |  | $ 0 |  | 0 |
FHLBC stock |  |  | 7,100,000 |  |  |
Principal balance of loans collateralized |  |  | 545,000,000.0 |  |  |
Combined collateral value |  |  | 396,900,000 |  |  |
Amount available for additional borrowings |  |  | 315,900,000 |  |  |
Subordinated debentures |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Total borrowings |  |  | 59,233,000 |  | 59,212,000 |
Notes payable and other borrowings |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Total borrowings |  |  | 17,992,000 |  | 19,074,000 |
Junior subordinated debentures |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Total borrowings |  |  | 25,773,000 |  | 25,773,000 |
Senior notes |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Interest rate (as a percent) |  |  |  | 5.75% |  |
Senior notes |  |  | 44,500,000 |  | 44,500,000 |
Debt Instrument, Term |  |  |  | 10 years |  |
Interest rate term |  |  |  | 5 years |  |
Debt issuance costs |  |  | $ 494,000 |  | 520,000 |
Amortization period for deferred financing costs |  |  | 10 years |  |  |
Total borrowings |  |  | $ 44,506,000 |  | $ 44,480,000 |
Senior notes | Debt Instrument, Variable Rate Base LIBOR [Member] |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Basis points added to reference rate (as a percent) |  |  |  | 385.00% |  |
Term Debt |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Proceeds from term note |  | $ 20,000,000.0 | $ 12,000,000.0 |  |  |
Debt term |  | 3 years |  |  |  |
Subordinated Notes Due 2031 |  |  |  |  |  |
Borrowings |  |  |  |  |  |
Interest rate (as a percent) | 3.50% |  |  |  |  |
Face amount | $ 60,000,000.0 |  |  |  |  |

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