Executive Benefit Agreement, Employee Savings Plans and Collective Bargaining Agreements - Executive Benefit Agreements (Detail) - USD ($) $ in Thousands	Dec. 31, 2020	Dec. 31, 2019
Compensation Related Costs [Abstract]
Total undiscounted death benefit	$ 2,500	$ 2,500
Total accrued death benefit	$ 2,539	$ 2,564