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Business Combination & Asset Purchase - Additional Information (Detail) |  |  |  | 3 Months Ended | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | ---
Nov. 16, 2020 USD ($) shares | Jan. 01, 2019 USD ($) Office $ / shares shares | Dec. 13, 2013 USD ($) | Jun. 30, 2019 Loan | Dec. 31, 2020 USD ($) shares | Dec. 31, 2019 USD ($) shares | Dec. 31, 2018 USD ($) | Nov. 30, 2020 USD ($) Client | Jan. 01, 2020 USD ($)
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Common stock, shares outstanding | shares |  |  |  |  | 12,230,000 | 12,230,000 |  |  |
Business combination, acquisition related costs |  |  |  |  |  | $ 1,280,000 | $ 742,100 |  |
Business combination, acquisition related costs percentage |  |  |  |  |  |  | 98.40% |  |
Recognition of core deposit intangible asset with acquired purchase |  |  |  |  |  | $ 3,900,000 |  |  |
Remaining economic useful life |  |  |  |  |  | 7 years |  |  |
Goodwill |  |  |  |  | $ 47,340,000 | $ 47,340,000 |  |  |
Fair value of assets acquired |  |  |  |  | 257,200,000 |  |  |  |
Gross principal and contractual interest |  |  |  |  | 359,200,000 |  |  |  |
Acquisition expected to be uncollectible |  |  |  |  | $ 4,700,000 |  |  |  |
Loan receivable weighted average life |  |  |  |  | 70 months |  |  |  |
Business combination, premises and equipment written down value |  |  |  |  | $ 1,200,000 |  |  |  |
Business combination, average remaining life |  |  |  |  | 16 years 9 months |  |  |  |
Fair value for certificate of deposit, valuation amount |  |  |  |  | $ 500,000 |  |  |  |
Fair value for certificate of deposit, amortization period |  |  |  |  | 1 year 6 months |  |  |  |
Fair value of Federal Home Loan Bank (FHLB) advances, valuation amount |  |  |  |  | $ 1,300,000 |  |  |  |
Fair value of Federal Home Loan Bank (FHLB) advances, amortization period |  |  |  |  | 2 years 3 months 18 days |  |  |  |
Fair value adjustment of loans acquired and accounted |  | $ 2,118,000 |  |  | $ 0 | 62,000 |  |  | $ 62,000
Number of commercial purchased credit impaired loans paid off | Loan |  |  |  | 2 |  |  |  |  |
Discount recognized at acquisition related to commercial purchased credit-impaired loans |  |  |  |  |  | 1,985,000 |  |  |
Amortization expense |  |  |  |  | 720,000 | 727,000 | $ 167,000 |  |
Core Deposits [Member] | Custar [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Recognition of core deposit intangible asset with acquired purchase |  |  | $ 1,170,000 |  |  |  |  |  |
Customer Lists [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Amortization expense |  |  |  |  | $ 16,000 |  |  |  |
Consulting Fees [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Business combination, acquisition related costs |  |  |  |  |  | 19,300 | 340,000 |  |
Other General and Administrative Expenses [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Business combination, acquisition related costs |  |  |  |  |  | 199,800 | 331,500 |  |
Data Processing [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Business combination, acquisition related costs |  |  |  |  |  | 867,600 | $ 58,600 |  |
Employee Benefits [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Business combination, acquisition related costs |  |  |  |  |  | 163,000.0 |  |  |
ATM Expense [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Business combination, acquisition related costs |  |  |  |  |  | 31,400 |  |  |
Bank of Geneva [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Number of full-service offices | Office |  | 6 |  |  |  |  |  |  |
Pro-forma operating revenue, net of tax |  |  |  |  |  | 7,400,000 |  |  |
Limberlost Bancshares, Inc. [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Common stock issued in exchange of each outstanding share | shares |  | 1,830,000 |  |  |  |  |  |  |
Cash payment for exchange of each share | $ / shares |  | $ 8,465.00 |  |  |  |  |  |  |
Common stock, shares outstanding | shares |  | 1,000 |  |  |  |  |  |  |
Share price | $ / shares |  | $ 38.49 |  |  |  |  |  |  |
Total consideration for acquisition |  | $ 78,902,000 |  |  |  |  |  |  |
Cash paid for acquisition |  | 8,465,000 |  |  |  | $ 8,465,000 |  |  |
Stock issued for acquisition |  | 70,437,000 |  |  |  |  |  |  |
Goodwill |  | 43,266,000 |  |  |  |  |  |  |
Limberlost Bancshares, Inc. [Member] | Core Deposits [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Recognition of core deposit intangible asset with acquired purchase |  | $ 3,900,000 |  |  |  |  |  |  |
Remaining economic useful life |  | 7 years |  |  |  |  |  |  |
Adams County Financial Resources |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Common stock issued in exchange of each outstanding share | shares | 40,049 |  |  |  |  |  |  |  |
Total consideration for acquisition | $ 825,000 |  |  |  |  |  |  |  |
Stock issued for acquisition | 825,000 |  |  |  |  |  |  |  |
Assets under management amount |  |  |  |  |  |  |  | $ 83,000 |
Number of clients assets under management | Client |  |  |  |  |  |  |  | 450 |
Increase to noninterest income | 500,000 |  |  |  |  |  |  |  |
Adams County Financial Resources | Customer Lists [Member] |  |  |  |  |  |  |  |  |
Business Acquisition [Line Items] |  |  |  |  |  |  |  |  |
Recognition of core deposit intangible asset with acquired purchase | $ 800,000 |  |  |  |  |  |  |  |
Remaining economic useful life | 6 years 6 months |  |  |  |  |  |  |  |

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