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Borrowings - Additional information (Details) | 12 Months Ended |
--- | --- | ---
Dec. 31, 2017 USD ($) item | Dec. 31, 2016 USD ($)
Borrowings |  |
Threshold percentage of stockholders' equity | 10.00% |
Borrowings at FHLBC as percentage of total assets | 35.00% |
Bank owned FHLBC stock | $ 5,400,000 | $ 3,100,000
Fair value of securities collateralized | 80,900,000 |
Principal balance of loans collateralized | 277,400,000 |
Maximum borrowing capacity | 286,300,000 |
Amount available for additional borrowings | 132,000,000 |
Senior notes | 44,058,000 | 43,998,000
Debt issuance costs | 739,000 | 787,000
Total borrowings | 246,615,000 | 197,304,000
Securities sold under repurchase agreements |  |
Borrowings |  |
Carrying amount of securities secured | 29,900,000 | 25,700,000
Fair value of the pledged collateral | $ 40,000,000 | 43,000,000
Number of customers having secured balances exceeding specified percentage of stockholders equity | item | 0 |
Total borrowings | $ 29,918,000 | $ 25,715,000
Securities sold under repurchase agreements | Minimum |  |
Borrowings |  |
Maturity | 1 day |
Securities sold under repurchase agreements | Maximum |  |
Borrowings |  |
Maturity | 90 days |
FHLBC advances |  |
Borrowings |  |
Semi annual interest rate |  | 0.70%
FHLBC advance amount | $ 115,000,000 |
Total borrowings | $ 115,000,000 | $ 70,000,000
FHLB advances at 1.42 % |  |
Borrowings |  |
Semi annual interest rate | 1.42% |
FHLBC advance amount | $ 110,000,000 |
FHLB advances at 1.44 % |  |
Borrowings |  |
Semi annual interest rate | 1.44% |
FHLBC advance amount | $ 5,000,000 |
Junior subordinated debentures |  |
Borrowings |  |
Total borrowings | $ 57,639,000 | 57,591,000
Senior Notes. |  |
Borrowings |  |
Semi annual interest rate | 5.75% |
Debt Instrument, Term | 10 years |
Interest rate term | 5 years |
Debt issuance costs | $ 942,000 | 1,000,000
Total borrowings | $ 44,058,000 | $ 43,998,000
Senior Notes. | Three month LIBOR |  |
Borrowings |  |
Basis points added to reference rate (as a percent) | 385.00% |

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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. + Details
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- Definition Represents the number of customers having secured balances exceeding specified percentage of stockholders equity. + References No definition available. + Details
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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. + Details
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- Definition Contractual interest rate for funds borrowed, under the debt agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(a)(1)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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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. + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 835 -SubTopic 30 -Section 45 -Paragraph 3 -URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28555-108399 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.17) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition Amount of advances from the Federal Home Loan Bank (FHLB). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 470 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6479118&loc=d3e64650-112822 + Details
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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). + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 325 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=75031641&loc=d3e63345-112809 + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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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. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 860 -SubTopic 30 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=66007379&loc=d3e113888-111728 + Details
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