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Income Taxes - Additional Information (Details) - USD ($) |  |  | 3 Months Ended | 12 Months Ended
--- | --- | --- | --- | ---
Jul. 01, 2017 | Jun. 30, 2017 | Dec. 31, 2017 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Income Tax [Line Items] |  |  |  |  |  |
Corporate federal income tax rate |  |  |  | 21.00% | 21.00% | 35.00%
Net income tax expense (benefit) |  |  | $ 7,200,000 |  | $ (760,000) |
Reclassification of certain income tax effects from accumulated other comprehensive income (loss) |  |  |  |  | (763,000) |
Deferred tax assets, net |  |  |  | $ 38,300,000 | 35,600,000 |
Operating loss carryforwards, limitations on use |  |  |  | Pursuant to Sections 382 and 383 of the Internal Revenue Code, annual use of net operating loss and credit carryforwards may be limited in the event a cumulative change in ownership of more than 50 percent occurs within a threeyear period. |  |
Cumulative change in ownership Percentage |  |  |  | 50.00% |  |
Period for cumulative change in ownership |  |  |  | 3 years |  |
Estimated net operating losses available each year |  |  |  | $ 756,000 |  |
Oak Park River Forest Bankshares, Inc. |  |  |  |  |  |
Income Tax [Line Items] |  |  |  |  |  |
Increase in deferred tax assets, net |  |  |  | 5,900,000 |  |
Estimated net operating losses available each year |  |  |  | 781,000 |  |
Net operating loss carryforwards |  |  |  | 4,300,000 |  |
ASU 2018-02 |  |  |  |  |  |
Income Tax [Line Items] |  |  |  |  |  |
Reclassification of certain income tax effects from accumulated other comprehensive income (loss) |  |  |  | 763,000 |  |
State |  |  |  |  |  |
Income Tax [Line Items] |  |  |  |  |  |
Net operating loss carryforwards |  |  |  | $ 307,705,000 | $ 340,999,000 |
Illinois | State |  |  |  |  |  |
Income Tax [Line Items] |  |  |  |  |  |
Corporate income tax rate | 7.00% | 5.25% |  |  |  |
State income tax benefit due to increased value of deferred tax asset related to net loss deduction |  |  |  |  |  | $ 4,800,000

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