Summary of Significant Accounting Policies - Rollforward of Deferred Revenue (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Accounting Policies [Abstract]
Beginning Balance	$ (63,646)	$ (57,763)
Revenue recognized that was included in deferred revenue at the beginning of the period	40,811	39,352
Consideration received in advance of services performed net of revenue recognized in the current period	(46,719)	(44,051)
Other	(78)	(1,184)
Ending Balance	$ (69,632)	$ (63,646)