Overview and Basis of Presentation - Schedule of Corrections to Prior Period Adjustments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Total revenue	$ 233,599	$ 62,807	$ 323,767	$ 387,532
Services
Total revenue	182,964	43,437	254,170	333,052
Costs and expenses	150,983	51,465	283,403	393,101
Cost of Services
Costs and expenses		51,465		393,101
GES
Total revenue	$ 116,044	13,992	$ 160,109	319,930
Previously Reported | Services
Total revenue		43,702		335,383
Previously Reported | Cost of Services
Costs and expenses		51,730		395,432
Revision of Prior Period, Error Correction, Adjustment | GES | Services
Total revenue		(265)		(2,331)
Revision of Prior Period, Error Correction, Adjustment | GES | Cost of Services
Costs and expenses		$ 265		$ 2,331