Summary of Significant Accounting Policies - Company's Income from Investments Held in Employee Deferred Compensation Trusts (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accounting Policies [Abstract]
Dividend income	$ (2,556)	$ (1,055)	$ (2,848)	$ (1,460)
Realized and unrealized (gains) losses	(25,254)	(47,872)	(36,949)	(7,091)
(Income) loss from investments held in employee deferred compensation trusts	$ (27,810)	$ (48,927)	$ (39,797)	$ (8,551)