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Share-Based Compensation - Additional Information (Details) - USD ($) |  |  |  |  | 1 Months Ended | 12 Months Ended |
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May 15, 2019 | Apr. 30, 2019 | Oct. 03, 2017 | Jul. 06, 2017 | Feb. 29, 2020 | Oct. 31, 2014 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Jun. 30, 2017
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Common stock, voting par value |  |  |  |  |  |  | $ 0.01 | $ 0.01 |  |  |  |
Proceeds from the exercise of stock options |  |  |  |  |  |  | $ 3,146,000 | $ 2,340,000 |  |  |  |
Oak Park River Forest Bankshares, Inc. |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Consideration paid in cash | $ 4,200,000 | $ 6,163,000 |  |  |  |  |  |  |  |  |  |
Business combination conversion of outstanding options | 35,870 |  |  |  |  |  |  |  |  |  |  |
Performance-based Restricted Shares | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shares of restricted voting common stock granted |  |  |  |  | 31,928 |  |  |  |  |  |  |
Period for number of shares earned under return on average assets |  |  |  |  | 3 years |  |  |  |  |  |  |
Performance Options Grants |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Options vested |  |  | 414,894 |  |  |  |  |  |  |  |  |
Common Stock |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock in connection with restricted stock awards, shares |  |  |  |  |  |  | 180,664 | 129,057 | 70,398 |  |  |
Number of options exercised |  |  |  |  |  |  | 241,211 | 205,152 |  |  |  |
Common Stock | Restricted Shares | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shares of restricted voting common stock granted |  |  |  |  | 172,660 |  |  |  |  |  |  |
Common stock, voting par value |  |  |  |  | $ 0.01 |  |  |  |  |  |  |
Common Stock | Restricted Shares | Each Anniversary of Grant Date Over Four Years | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  | 4 years |  |  |  |  |  |  |
Shares vest on grant date |  |  |  |  | 101,946 |  |  |  |  |  |  |
Common Stock | Restricted Shares | Each Anniversary of Grant Date Vest Over Three Years | Subsequent Event |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  | 3 years |  |  |  |  |  |  |
Shares vest on grant date |  |  |  |  | 38,786 |  |  |  |  |  |  |
Omnibus Plan |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of common stock reserved for issuance |  |  |  |  |  |  |  |  |  |  |  | 1,550,000
Number of common shares available for future grants |  |  |  |  |  |  | 1,169,881 |  |  |  |  |
Omnibus Plan | Restricted Shares |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  |  |  |  |  | 4 years |  |  |
Shares of restricted voting common stock granted |  |  |  |  |  |  | 210,622 |  |  |  |  |
Restricted shares vested |  |  |  |  |  |  | 48,491 | 2,975 | 0 |  |  |
Fair value of restricted shares, vested |  |  |  |  |  |  | $ 900,000 | $ 62,000 |  |  |  |
Restricted shares vested |  |  |  |  |  |  | 48,491 | 2,975 | 0 |  |  |
Fair value of unvested restricted stock awards |  |  |  |  |  |  | $ 6,400,000 |  |  |  |  |
Number of shares outstanding |  |  |  |  |  |  | 328,653 | 196,480 |  |  |  |
Omnibus Plan | Performance-based Restricted Shares |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shares of restricted voting common stock granted |  |  |  |  |  |  | 20,975 | 11,165 |  |  |  |
Period for number of shares earned under return on average assets |  |  |  |  |  |  | 3 years | 3 years |  |  |  |
Minimum target percentage in assets of peer group consisting publicly-traded bank holding companies |  |  |  |  |  |  |  | 50.00% |  |  |  |
Maximum target percentage in assets of peer group consisting publicly-traded bank holding companies |  |  |  |  |  |  |  | 200.00% |  |  |  |
Omnibus Plan | Performance-based Restricted Shares | Threshold performance |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage of target number of shares to be earned |  |  |  |  |  |  |  | 25.00% |  |  |  |
Omnibus Plan | Performance-based Restricted Shares | 50th Percentile Performance |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage of target number of shares to be earned |  |  |  |  |  |  |  | 100.00% |  |  |  |
Omnibus Plan | Performance-based Restricted Shares | 75th Percentile Performance |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Percentage of target number of shares to be earned |  |  |  |  |  |  |  | 125.00% |  |  |  |
Omnibus Plan | Common Stock |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Issuance of common stock in connection with restricted stock awards, shares |  |  |  | 58,900 |  |  |  |  | 11,898 |  |  |
Omnibus Plan | Common Stock | Restricted Shares |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shares of restricted voting common stock granted |  |  |  |  |  |  | 189,647 | 131,157 |  |  |  |
Common stock, voting par value |  |  |  |  |  |  | $ 0.01 | $ 0.01 |  |  |  |
Shares vested |  |  |  |  |  |  | 4,571 |  |  |  |  |
Omnibus Plan | Common Stock | Restricted Shares | Each Anniversary of Grant Date Over Four Years |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  |  |  | 4 years | 4 years |  |  |  |
Shares vest on grant date |  |  |  |  |  |  | 111,823 | 102,559 |  |  |  |
Omnibus Plan | Common Stock | Restricted Shares | Each Anniversary of Grant Date Vest Over Three Years |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  |  |  | 3 years | 3 years |  |  |  |
Shares vest on grant date |  |  |  |  |  |  | 72,570 | 15,165 |  |  |  |
Omnibus Plan | Common Stock | Restricted Shares | First Anniversary of Grant Date |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Shares vest on grant date |  |  |  |  |  |  | 683 | 2,268 |  |  |  |
MBG Plan |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of options granted |  |  |  |  |  |  |  |  | 0 |  |  |
Number of options exercised |  |  |  |  |  |  |  |  | 0 |  |  |
BYB Plan |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of common shares available for future grants |  |  |  |  |  |  |  |  |  |  |  | 0
Number of options granted |  |  |  |  |  |  |  |  | 0 | 212,400 | 1,634,568 |
Number of options exercised |  |  |  |  |  |  | 127,997 | 148,748 | 0 |  |  |
Number of shares outstanding |  |  |  |  |  |  | 1,410,075 | 1,598,872 |  |  |  |
Options vested |  |  |  |  |  |  | 17,500 |  |  |  |  |
Proceeds from the exercise of stock options |  |  |  |  |  |  | $ 1,900,000 | $ 1,700,000 |  |  |  |
Tax benefit from exercise of stock options |  |  |  |  |  |  | $ 145,000 | $ 449,000 |  |  |  |
BYB Plan | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of common shares available for future grants |  |  |  |  |  | 2,476,122 |  |  |  |  |  |
BYB Plan | Time Options Grants |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award contractual term |  |  |  |  |  | 10 years |  |  |  |  |  |
BYB Plan | Time Options Grants | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  |  | 5 years |  |  |  |  |  |
BYB Plan | Time Options Grants | Minimum |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  |  | 1 year |  |  |  |  |  |
BYB Plan | Performance Options Grants |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award contractual term |  |  |  |  |  | 10 years |  |  |  |  |  |
BYB Plan | Performance Options Grants | Maximum |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  |  | 5 years |  |  |  |  |  |
BYB Plan | Performance Options Grants | Minimum |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Award vesting period |  |  |  |  |  | 1 year |  |  |  |  |  |
FEB Plan |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of options exercised |  |  |  |  |  |  | 113,214 | 56,404 |  |  |  |
Number of shares outstanding |  |  |  |  |  |  | 511,169 | 624,383 |  |  |  |
Proceeds from the exercise of stock options |  |  |  |  |  |  | $ 1.3 | $ 601,000 |  |  |  |
Tax benefit from exercise of stock options |  |  |  |  |  |  | $ 253,000 | $ 168,000 |  |  |  |
Conversion calculation percentage |  |  |  |  |  |  | 472.50% |  |  |  |  |
FEB Plan | Restricted Shares |  |  |  |  |  |  |  |  |  |  |  |
Share Based Compensation Arrangement By Share Based Payment Award [Line Items] |  |  |  |  |  |  |  |  |  |  |  |
Number of shares outstanding |  |  |  |  |  |  | 0 |  |  |  |  |

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- Definition The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan). + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c)(2)(iii)(1) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Fair value of share-based awards for which the grantee gained the right by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (d)(2) -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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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. + Details
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- Definition The difference between the maximum number of shares (or other type of equity) authorized for issuance under the plan (including the effects of amendments and adjustments), and the sum of: 1) the number of shares (or other type of equity) already issued upon exercise of options or other equity-based awards under the plan; and 2) shares (or other type of equity) reserved for issuance on granting of outstanding awards, net of cancellations and forfeitures, if applicable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 718 -SubTopic 10 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901 + Details
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- Definition Gross number of share options (or share units) granted during the period. + References No definition available. + Details
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