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Benefit Plans - Components of Accumulated Other Comprehensive Loss (Gain) (Detail) - USD ($)
$ in Thousands
Dec. 31, 2020
Dec. 31, 2019
Pension    
Defined Benefit Plan Disclosure [Line Items]    
Unrecognized prior service cost $ 0 $ 0
Unrecognized net actuarial loss (gain) 9,026 10,346
Total accumulated other comprehensive loss (gain) 9,026 10,346
Post-retirement    
Defined Benefit Plan Disclosure [Line Items]    
Unrecognized prior service cost 0 0
Unrecognized net actuarial loss (gain) (8,055) (3,621)
Total accumulated other comprehensive loss (gain) $ (8,055) $ (3,621)