Directors Retirement Plan - Status of Directors Retirement Plan (Detail) - Director - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Accrued plan cost included in other liabilities	$ 655	$ 646
Recognized in accumulated other comprehensive income
Net actuarial loss	36	64
Amounts not recognized as a component of net postretirement benefit	$ 36	$ 64

Amount, after tax, of accumulated other comprehensive (income) loss for defined benefit plan, that has not been recognized in net periodic benefit cost (credit).

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Amount of actuarial present value of benefits attributed to employee service rendered, excluding assumptions about future compensation level.

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Amount, after tax, of accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan, that has not been recognized in net periodic benefit (cost) credit.

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