Borrowings - Additional information (Details)	3 Months Ended	6 Months Ended
Dec. 31, 2016 USD ($)	Jun. 30, 2017 USD ($) item
Borrowings
Semi annual interest rate	5.75%
Bank owned FHLBC stock	$ 3,100,000	$ 3,800,000
Subordinated Debt.	45,000,000
Senior debt	500,000
Senior notes issuance and cash on hand	45,000,000
Senior notes	$ 43,998,000	44,008,000
Debt Instrument, Term	10 years
Interest rate term	5 years
Senior note debt issuance costs	$ 1,000,000
Total borrowings	$ 197,304,000	212,984,000
Three month LIBOR
Borrowings
Basis points added to reference rate (as a percent)	385.00%
Securities sold under repurchase agreements
Borrowings
Carrying amount of securities secured	$ 25,700,000	36,400,000
Fair value of the pledged collateral	43,000,000	$ 44,400,000
Number of customers having secured balances exceeding specified percentage of stockholders equity \| item		0
Total borrowings	25,715,000	$ 36,361,000
Securities sold under repurchase agreements \| Minimum
Borrowings
Threshold percentage of stockholders' equity		10.00%
FHLBC advances
Borrowings
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 advance amount	70,000,000	$ 75,000,000
Bank owned FHLBC stock		3,800,000
Fair value of securities collateralized		100,000,000
Principal balance of loans collateralized		176,700,000
Combined collateral value		205,600,000
Amount available for additional borrowings		94,300,000
Total borrowings	70,000,000	75,000,000
Junior subordinated debentures
Borrowings
Total borrowings	$ 57,591,000	$ 57,615,000

Represents the period for which the interest rate is applicable.

No definition available.

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- Definition

Represents the amount of borrowings from Federal Home Loan Bank as a percentage of book value of certain mortgage loans.

+ References

No definition available.

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- Definition

Represents the amount of borrowings from Federal Home Loan Bank as a percentage of total assets.

+ References

No definition available.

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- Definition

Represents the principal balance of loans pledged as collateral in support of federal home loan bank advances outstanding.

+ References

No definition available.

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- Definition

Represents the fair value of securities pledged as collateral in support of federal home loan bank advances outstanding

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No definition available.

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- Definition

Represents the number of customers having secured balances exceeding specified percentage of stockholders equity.

+ References

No definition available.

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- Definition

Represents the amount received from senior notes issued plus cash on hand.

+ References

No definition available.

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- Definition

Represents the amount of senior debt with maturities beyond one year or beyond the operating cycle if longer.

+ References

No definition available.

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- Definition

Represents the threshold percentage which the entity uses for disclosure about the customer holding secured balances.

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No definition available.

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- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

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- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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-SubTopic 10
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-Subparagraph (SX 210.5-02.22(a)(1))
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- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

No definition available.

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- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

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- Definition

Amount of unused borrowing capacity under the long-term financing arrangement that is available to the entity as of the balance sheet date.

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-Name Accounting Standards Codification
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- Definition

Represents the aggregate of total long-term debt, including current maturities and short-term debt.

+ References

No definition available.

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- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

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- Definition

Amount of advances from the Federal Home Loan Bank (FHLB).

+ References

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- Definition

Amount of the collateral pledged in support of federal home loan bank advances outstanding.

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- Definition

Federal Home Loan Bank (FHLB) stock represents an equity interest in a FHLB. It does not have a readily determinable fair value because its ownership is restricted and it lacks a market (liquidity).

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- Definition

The fair value, as of the date of each statement of financial position presented, of securities which are owned but transferred to serve as collateral for the payment of repurchase agreements, and that are reclassified and separately reported in the statement of financial position because the transferee has the right by contract or custom to sell or re-pledge them.

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The carrying amount as of the date of the latest financial statement presented of securities which are owned but transferred to serve as collateral for repurchase agreements, and for which the transferee does not have the right by contract or custom to sell or re-pledge them to an unrelated party.

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of Notes with the highest claim on the assets of the issuer in case of bankruptcy or liquidation (with maturities initially due after one year or beyond the operating cycle if longer). Senior note holders are paid off in full before any payments are made to junior note holders.

+ References

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- Definition

Including the current and noncurrent portions, carrying value as of the balance sheet date of subordinated debt (with initial maturities beyond one year or beyond the operating cycle if longer). Subordinated debt places a lender in a lien position behind debt having a higher priority of repayment in liquidation of the entity's assets.

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