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Borrowings - Additional information (Details) | 12 Months Ended
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Dec. 31, 2015 USD ($) item | Dec. 31, 2014 USD ($) | Dec. 31, 2013 USD ($)
Borrowings |  |  |
Bank owned FHLBC stock | $ 3,700,000 | $ 4,300,000 |
Total borrowings | 152,948,000 | 169,914,000 |
Securities sold under repurchase agreements |  |  |
Borrowings |  |  |
Carrying amount of securities secured | 34,100,000 | 21,000,000 |
Fair value of the pledged collateral | $ 45,400,000 | 43,400,000 |
Number of customers having secured balances exceeding specified percentage of stockholders equity | item | 0 |  |
Total borrowings | $ 34,070,000 | 21,036,000 |
Additional information related to repurchase agreements |  |  |
Average daily balance during the year | $ 28,194,000 | $ 26,093,000 | $ 23,313,000
Average interest rate during the year (as a percent) | 0.01% | 0.01% | 0.01%
Maximum month-end balance during the year | $ 34,785,000 | $ 38,133,000 | $ 30,510,000
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 |  |  |
Borrowings at FHLBC as percentage of total assets | 35.00% |  |
Borrowings at FHLBC as percentage of book value of certain mortgage loans | 60.00% |  |
Debt Instrument, Interest Rate, Stated Percentage | 0.16% |  |
Bank owned FHLBC stock | $ 3,700,000 |  |
Fair value of securities collateralized | 98,800,000 |  |
Principal balance of loans collateralized | 169,700,000 |  |
Combined collateral value | 190,700,000 |  |
Amount available for additional borrowings | 174,400,000 |  |
Total borrowings | 15,000,000 | $ 45,000,000 |
Subordinated debt |  |  |
Borrowings |  |  |
Face amount | 45,000,000 |  |
Total borrowings | $ 45,000,000 | 45,000,000 |
Subordinated debt | LIBOR |  |  |
Borrowings |  |  |
Variable interest rate base | three-month LIBOR |  |
Basis points added to reference rate (as a percent) | 1.50% |  |
Notes payable and other borrowings |  |  |
Borrowings |  |  |
Total borrowings | $ 500,000 | 500,000 |
Correspondent Bank |  |  |
Borrowings |  |  |
Maximum borrowing capacity | $ 45,500,000 |  |
Senior debt facility | LIBOR |  |  |
Borrowings |  |  |
Basis points added to reference rate (as a percent) | 0.90% |  |
Senior debt facility | Prime rate |  |  |
Borrowings |  |  |
Variable interest rate base | prime |  |
Term debt |  |  |
Borrowings |  |  |
Maximum borrowing capacity | $ 500,000 |  |
Basis points added to reference rate (as a percent) | 2.00% |  |
Total borrowings | $ 500,000 |  |
Junior subordinated debentures |  |  |
Borrowings |  |  |
Total borrowings | $ 58,378,000 | $ 58,378,000 |

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