Stock-based Compensation Plans - Additional Information 4 (Detail) - USD ($) shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019	Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation plan vesting period			3 years
Deferred compensation plan	$ (6,237,000)	$ 8,871,000	$ (10,287,000)	$ 16,432,000
Shares held in rabbi trust total	6.1		6.1		3.2
Vested shares held in rabbi trust	4.4		4.4		2.7
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	$ 90,000	$ 90,000	$ 275,000	$ 275,000