Summary of Significant Accounting Policies - Company's Income from Investments Held in Employee Deferred Compensation Trusts (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Accounting Policies [Abstract]
Dividend income	$ (294)	$ (405)
Realized and unrealized (gains) losses	(11,694)	40,781
(Income) loss from investments held in employee deferred compensation trusts	$ (11,988)	$ 40,376