Summary of Significant Accounting Policies - Company's Income from Investments Held in Employee Deferred Compensation Trusts (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accounting Policies [Abstract]
Dividend income	$ (4,565)	$ (443)	$ (7,414)	$ (1,887)
Realized and unrealized (gains) losses	6,324	(25,652)	(30,625)	(32,743)
(Income) loss from investments held in employee deferred compensation trusts	$ 1,759	$ (26,095)	$ (38,039)	$ (34,630)