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Recent Developments Including Mergers and Acquisitions - Additional Information (Detail) |  |  |  |  |  | 12 Months Ended |  |
--- | --- | --- | --- | --- | --- | --- | --- | ---
Mar. 05, 2020 USD ($) | Dec. 31, 2019 USD ($) | Aug. 15, 2019 USD ($) | Aug. 31, 2018 USD ($) ft² Floor | Jan. 11, 2018 USD ($) Community Location | Dec. 31, 2020 USD ($) | Dec. 31, 2018 USD ($) | Dec. 14, 2018
Business Combination Separately Recognized Transactions [Line Items] |  |  |  |  |  |  |  |
Goodwill |  | $ 148,604,000 |  |  |  | $ 149,922,000 | $ 79,749,000 |
Number of additional banking communities | Community |  |  |  |  | 5 |  |  |
BFTower LLC [Member] | ParcFirst LLC [Member] |  |  |  |  |  |  |  |
Business Combination Separately Recognized Transactions [Line Items] |  |  |  |  |  |  |  |
Ownership interest acquired |  | 50.00% |  |  |  |  |  |
Payment to acquire ownership interest |  | $ 1,500,000 |  |  |  |  |  |
COVID 19 [Member] |  |  |  |  |  |  |  |
Business Combination Separately Recognized Transactions [Line Items] |  |  |  |  |  |  |  |
Loans modification |  |  |  |  |  | $ 81,700,000 |  |
Citizens Bankshares, Inc [Member] |  |  |  |  |  |  |  |
Business Combination Separately Recognized Transactions [Line Items] |  |  |  |  |  |  |  |
Date of acquisition | Mar. 05, 2020 |  |  |  |  |  |  |
Total assets acquired | $ 47,800,000 |  |  |  |  |  |  |
Loans | 22,900,000 |  |  |  |  |  |  |
Deposits | 45,000,000.0 |  |  |  |  |  |  |
Purchase price | 2,900,000 |  |  |  |  |  |  |
Intangibles assets, net | 206,000 |  |  |  |  |  |  |
Goodwill | $ 1,300,000 |  |  |  |  |  |  |
Pegasus Bank [Member] |  |  |  |  |  |  |  |
Business Combination Separately Recognized Transactions [Line Items] |  |  |  |  |  |  |  |
Date of acquisition |  |  | Aug. 15, 2019 |  |  |  |  |
Total assets acquired |  |  | $ 651,100,000 |  |  |  |  |
Loans |  |  | 389,900,000 |  |  |  |  |
Deposits |  |  | 603,900,000 |  |  |  |  |
Purchase price |  |  | 123,500,000 |  |  |  |  |
Intangibles assets, net |  |  | 9,900,000 |  |  |  |  |
Goodwill |  |  | $ 68,900,000 |  |  |  |  |
Cotter Ranch Tower [Member] | BFTower LLC [Member] |  |  |  |  |  |  |  |
Business Combination Separately Recognized Transactions [Line Items] |  |  |  |  |  |  |  |
Date of acquisition |  |  |  | Aug. 31, 2018 |  |  |  |
Purchase price |  |  |  | $ 21,000,000.0 |  |  |  |
Number of square feet | ft² |  |  |  | 507,000 |  |  |  |
Number of floors | Floor |  |  |  | 36 |  |  |  |
Percentage of property leased |  |  |  | 55.00% |  |  |  |
Percentage of occupancy |  |  |  | 35.00% |  |  |  |
Percentage of occupancy including leased space |  |  |  | 90.00% |  |  |  |
Renovations completion year |  |  |  | 2022 |  |  |  |
Renovations cost |  |  |  | $ 70,000,000 |  |  |  |
Tenant improvements |  |  |  | $ 10,000,000 |  |  |  |
Number of square feet to be occupied | ft² |  |  |  | 165,000 |  |  |  |
Cotter Ranch Tower [Member] | BFTower LLC [Member] | SFPG, LLC [Member] |  |  |  |  |  |  |  |
Business Combination Separately Recognized Transactions [Line Items] |  |  |  |  |  |  |  |
Ownership interest acquired |  |  |  |  |  | 49.00% |  | 42.60%
Payment to acquire ownership interest |  |  |  |  |  | $ 11,300,000 |  |
First Bank & Trust Company [Member] |  |  |  |  |  |  |  |
Business Combination Separately Recognized Transactions [Line Items] |  |  |  |  |  |  |  |
Date of acquisition |  |  |  |  | Jan. 11, 2018 |  |  |
Total assets acquired |  |  |  |  | $ 290,000,000 |  |  |
Loans |  |  |  |  | 247,000,000 |  |  |
Deposits |  |  |  |  | 251,000,000 |  |  |
Intangibles assets, net |  |  |  |  | 6,300,000 |  |  |
Goodwill |  |  |  |  | $ 19,100,000 |  |  |
First Bank of Chandler [Member] |  |  |  |  |  |  |  |
Business Combination Separately Recognized Transactions [Line Items] |  |  |  |  |  |  |  |
Date of acquisition |  |  |  |  | Jan. 11, 2018 |  |  |
Total assets acquired |  |  |  |  | $ 88,000,000 |  |  |
Loans |  |  |  |  | 66,000,000 |  |  |
Deposits |  |  |  |  | 79,000,000 |  |  |
Intangibles assets, net |  |  |  |  | 2,200,000 |  |  |
Goodwill |  |  |  |  | $ 6,600,000 |  |  |
Number of locations acquired | Location |  |  |  |  | 2 |  |  |

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