Business and Basis of Presentation - Narrative (Details) $ in Thousands	1 Months Ended	3 Months Ended		9 Months Ended
	May 31, 2021 USD ($)	Sep. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($) segment	Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Number of reportable segments | segment				3
Cash and cash equivalents, and restricted cash		$ 769,730	$ 553,715	$ 769,730	$ 553,715	$ 712,583	$ 280,836
Cash and cash equivalents		765,530		765,530		$ 712,583
Restricted cash		4,200		4,200
Proceeds from event cancellation insurance claims	$ 150,000
Gain on event cancellation insurance claims	$ 135,500	$ 0	$ 0	$ 135,545	$ 0