Stock-based Compensation Plans - Additional Information 4 (Detail) - USD ($) shares in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018	Dec. 31, 2018
Defined Benefit Plan Disclosure [Line Items]
Deferred compensation plan vesting period			3 years
Deferred compensation plan	$ 8,871,000	$ (223,000)	$ 16,432,000	$ 559,000
Shares held in rabbi trust total	3.2		3.2		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	$ 275,000	$ 275,000