Deferred Compensation - Additional Information (Detail) - USD ($)	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Disclosure Of Compensation Related Costs Sharebased Payments [Abstract]
Deferred compensation	$ 9,988,000	$ 15,140,000	$ (2,329,000)
Deferred compensation liability	$ 61,558,000	$ 59,031,000
Increase (decrease) in market price of common stock due to deferred compensation	$ 16.88	$ 28.44

Aggregate carrying value as of the balance sheet date of the liabilities for all deferred compensation arrangements. Represents currently earned compensation under compensation arrangements that is not actually paid until a later date.

No definition available.

Name:	us-gaap_DeferredCompensationLiabilityCurrentAndNoncurrent
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant