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Employee Benefit Plans - Additional Information (Detail) $ in Thousands | 12 Months Ended
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Dec. 31, 2019 USD ($) Employee shares | Dec. 31, 2018 USD ($) Employee shares | Dec. 31, 2017 USD ($) Employee shares
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Minimum percentage of eligible compensation on a pre-tax basis for eligible employees to save | 1.00% |  |
Employee contribution matching percentage | 50.00% |  |
Percentage of total eligible compensation, contribution by Bank, maximum limit | 4.00% |  |
Vesting percentage in participant's deferral contributions and employer matching contributions | 100.00% |  |
Vesting period | 6 years |  |
Employer matching contribution and the discretionary contribution | $ | $ 1,200 | $ 1,100 | $ 972
Restricted stock awards, shares issued | 38,100 | 33,000 | 32,000
Awards grants originated in 2014, 2015 and 2016 [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of employees, received the stock | Employee |  |  | 1
Four employees received shares from awards granted due to retirement |  |  | 640
Awards grants originated in 2016, 2017 and 2018 [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of employees, received the stock | Employee | 3 |  |
One employee received shares from awards granted due to retirement | 14,300 |  |
Restricted Stock Awards [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Vesting period | 3 years |  |
Stock issued to number of employees | Employee | 94 | 80 | 74
Shares vest under the plan | 100.00% | 100.00% | 100.00%
Shares forfeited due to employee termination | 3,220 | 2,620 | 1,080
Number of shares vested | 40,370 | 28,790 | 24,870
Number of employees, received the stock | Employee | 63 | 56 | 52
Compensation expense | $ | $ 1,100 | $ 745 | $ 507
One employee received shares from awards granted due to retirement | 14,300 |  | 640
Unrecognized compensation cost related to the nonvested portion of restricted stock awards under the plan | $ | $ 1,600 |  |
Unrecognized compensation cost related to the nonvested portion of restricted stock awards under the plan, period for recognition | 3 years |  |
Restricted Stock Awards [Member] | 2014 [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of shares vested |  |  | 24,230
Restricted Stock Awards [Member] | 2015 [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of shares vested |  | 28,790 |
Restricted Stock Awards [Member] | 2016 [Member] |  |  |
Share-based Compensation Arrangement by Share-based Payment Award [Line Items] |  |  |
Number of shares vested | 26,070 |  |

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