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Borrowings - Additional information (Details) | 12 Months Ended
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Dec. 31, 2016 USD ($) item | Dec. 31, 2015 USD ($) | Dec. 31, 2014 USD ($)
Borrowings |  |  |
Borrowings at FHLBC as percentage of total assets | 35.00% |  |
Bank owned FHLBC stock | $ 3,100,000 | $ 3,700,000 |
Fair value of securities collateralized | 63,300,000 |  |
Principal balance of loans collateralized | 168,200,000 |  |
Maximum borrowing capacity | 158,000,000 |  |
Amount available for additional borrowings | 51,700,000 |  |
Senior notes | 43,998,000 |  |
Total borrowings | 197,304,000 | 152,113,000 |
Securities sold under repurchase agreements |  |  |
Borrowings |  |  |
Carrying amount of securities secured | 25,700,000 | 34,100,000 |
Fair value of the pledged collateral | $ 43,000,000 | 45,400,000 |
Number of customers having secured balances exceeding specified percentage of stockholders equity | item | 0 |  |
Total borrowings | $ 25,715,000 | 34,070,000 |
Additional information related to repurchase agreements |  |  |
Average daily balance during the year | $ 34,016,000 | $ 28,194,000 | $ 26,093,000
Average interest rate during the year (as a percent) | 0.01% | 0.01% | 0.01%
Maximum month-end balance during the year | $ 46,606,000 | $ 34,785,000 | $ 38,133,000
Weighted average interest rate at year-end (as a percent) | 0.01% | 0.01% | 0.01%
Securities sold under repurchase agreements | Minimum |  |  |
Borrowings |  |  |
Maturity | 1 day |  |
Securities sold under repurchase agreements | Maximum |  |  |
Borrowings |  |  |
Maturity | 90 days |  |
FHLBC advances |  |  |
Borrowings |  |  |
Interest rate | 0.70% |  |
FHLBC advance amount | $ 70,000,000 |  |
Total borrowings | $ 70,000,000 | $ 15,000,000 |
Subordinated debt |  |  |
Borrowings |  |  |
Basis points added to reference rate (as a percent) | 150.00% |  |
Total borrowings | $ 45,000,000 | 45,000,000 |
Notes payable and other borrowings |  |  |
Borrowings |  |  |
Total borrowings |  | 500,000 |
Senior debt facility | LIBOR |  |  |
Borrowings |  |  |
Basis points added to reference rate (as a percent) | 90.00% |  |
Term debt |  |  |
Borrowings |  |  |
Total borrowings | $ 500,000 |  |
Junior subordinated debentures |  |  |
Borrowings |  |  |
Total borrowings | $ 57,591,000 | $ 57,543,000 |
Senior Notes. |  |  |
Borrowings |  |  |
Interest rate | 5.75% |  |
Debt Instrument, Term | 10 years |  |
Interest rate term | 5 years |  |
Senior note debt issuance costs | $ 1,000,000 |  |
Total borrowings | $ 43,998,000 |  |
Senior Notes. | LIBOR |  |  |
Borrowings |  |  |
Basis points added to reference rate (as a percent) | 385.00% |  |

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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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