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Acquisition of a Business - Additional Information (Details) - USD ($) |  |  |  | 12 Months Ended |
--- | --- | --- | --- | --- | ---
May 15, 2019 | Apr. 30, 2019 | May 31, 2018 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
Business Acquisition [Line Items] |  |  |  |  |  |  |
Goodwill |  |  |  | $ 148,353,000 | $ 128,177,000 | $ 54,562,000 | $ 51,975,000
Oak Park River Forest Bankshares, Inc. |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Business acquisition date of agreement |  |  |  | Apr. 30, 2019 |  |  |
Right to receive common stock upon conversion |  | 7.9321 |  |  |  |  |
Consideration paid in cash | $ 4,200,000 | $ 6,163,000 |  |  |  |  |
Common stock outstanding value per share |  | $ 33.375 |  |  |  |  |
Common stock issued price per share |  | $ 20.02 |  |  |  |  |
Issuance of common shares |  | 1,464,558 |  |  |  |  |
Value of common stock consideration |  | $ 29,300,000 |  |  |  |  |
Options to acquire common stock shares |  | 35,870 |  |  |  |  |
Option to acquire common stock value |  | $ 4,200,000 |  |  |  |  |
Total merger consideration |  | 35,483,000 |  |  |  |  |
Stock issuance costs |  | 585,000 |  |  |  |  |
Goodwill |  | $ 20,176,000 |  |  |  |  |
Fair value estimate of loans |  |  |  | $ 3,700,000 |  |  |
Fair value estimate of other assets |  |  |  | 25,000 |  |  |
Increase in deferred tax asset |  |  |  | 1,000,000 |  |  |
Increase in goodwill |  |  |  | 2,700,000 |  |  |
Oak Park River Forest Bankshares, Inc. | Non-interest Expense |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Acquisition advisory expenses |  |  |  | 2,300,000 |  |  |
Core system conversion expenses |  |  |  | $ 2,000,000 | 335,000 |  |
First Evanston Bancorp, Inc. |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Business acquisition date of agreement |  |  |  | May 31, 2018 |  |  |
Right to receive common stock upon conversion |  |  | 3.994 |  |  |  |
Consideration paid in cash |  |  | $ 27,004,000 |  |  |  |
Common stock outstanding value per share |  |  | $ 16.136 |  |  |  |
Common stock issued price per share |  |  | $ 21.62 |  |  |  |
Issuance of common shares |  |  | 6,682,850 |  |  |  |
Value of common stock consideration |  |  | $ 144,500,000 |  |  |  |
Options to acquire common stock shares |  |  | 144,090 |  |  |  |
Option to acquire common stock value |  |  | $ 7,600,000 |  |  |  |
Total merger consideration |  |  | 179,131,000 |  |  |  |
Stock issuance costs |  |  | 852,000 |  |  |  |
Goodwill |  |  | $ 73,615,000 |  |  |  |
Options to acquire conversion of common stock shares |  |  | 680,787 |  |  |  |
First Evanston Bancorp, Inc. | Non-interest Expense |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |
Acquisition advisory expenses |  |  |  |  | 1,700,000 | $ 1,300,000 |
Core system conversion expenses |  |  |  | $ 2,000,000 | $ 9,800,000 |  |

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- Definition This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 25 -Paragraph 23 -URI http://asc.fasb.org/extlink&oid=116868678&loc=d3e1043-128460 + Details
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- Definition Amount of consideration transferred, consisting of acquisition-date fair value of assets transferred by the acquirer, liabilities incurred by the acquirer, and equity interest issued by the acquirer. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 8 -URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6613-128477 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=35744584&loc=d3e6927-128479 Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 30 -Section 30 -Paragraph 7 -URI http://asc.fasb.org/extlink&oid=116859721&loc=d3e6578-128477 + Details
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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=77989000&loc=SL49117168-202975 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266 + Details
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