Employee Benefit Plans - Additional Information (Detail) $ in Thousands	12 Months Ended
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

Minimum percentage of eligible compensation on pre tax basis for eligible employees to save.

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Number of awards granted to four employees on retirement.

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Number of awards granted to one employee on retirement.

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Share based compensation arrangement by share based payment award equity instruments other than options share vested percentage.

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Share based compensation arrangement by share based payment award number of employee share issued.

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Share based compensation arrangement by share based payment award number of employees.

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Amount of expense for award under share-based payment arrangement. Excludes amount capitalized.

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Amount of discretionary contributions made by an employer to a defined contribution plan.

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Percentage of employees' gross pay for which the employer contributes a matching contribution to a defined contribution plan.

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Percentage of employer's matching contributions to a defined contribution plan that vests in a given year.

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Maximum percentage of employee gross pay the employee may contribute to a defined contribution plan.

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Weighted-average period over which cost not yet recognized is expected to be recognized for award under share-based payment arrangement, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days.

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Amount of cost to be recognized for nonvested award under share-based payment arrangement. Excludes share and unit options.

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Period over which grantee's right to exercise award under share-based payment arrangement is no longer contingent on satisfaction of service or performance condition, in 'PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents reported fact of one year, five months, and thirteen days. Includes, but is not limited to, combination of market, performance or service condition.

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The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

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The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

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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.

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Total number of shares issued during the period, including shares forfeited, as a result of Restricted Stock Awards.

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