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Stock-based Compensation Plans - Additional Information 4 (Detail) - USD ($)
shares in Millions
 3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]          
Deferred compensation plan vesting period     3 years    
Deferred compensation plan $ 11,142,000 $ (6,615,000) $ 7,561,000 $ 782,000  
Shares held in rabbi trust total 3.3   3.3   2.6
Vested shares held in rabbi trust 2.5   2.5   2.4
Post-Retirement Medical Plan          
Defined Benefit Plan Disclosure [Line Items]          
Estimated prior service cost amortized from accumulated other comprehensive income into general and administrative expense $ 92,000 $ 92,000 $ 185,000 $ 185,000