Employee Benefit Plans - Changes in Other Comprehensive Income (Loss) (Detail) - Defined Benefit Pension Plans - USD ($) $ in Thousands	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Net actuarial gain (loss) arising during the year	$ (934)	$ 1,330	$ (2,709)
Amortization of actuarial (gain) loss	1,412	1,584	1,937
Total	$ 478	$ 2,914	$ (772)

Amount, before tax, of reclassification adjustment from accumulated other comprehensive income (loss) for gain (loss) of defined benefit plan.

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