Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2023	Jun. 30, 2022
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	$ 283,107		$ 297,122		$ 691,064	$ 514,369
Costs and expenses:
Cost of services and product development - unallocated	487,418		424,535		922,557	801,568
Selling, general and administrative	680,168		604,911		1,337,258	1,222,815
Acquisition and integration charges	1,973		2,289		3,341	4,496
Gain from sale of divested operation	3,906		0		(135,410)	0
Operating income	283,107		297,122		691,064	514,369
Interest expense and other, net	(18,983)		(21,171)		(48,740)	(23,359)
Gain on event cancellation insurance claims	0		0		3,077	0
Less: Provision for income taxes	66,081		71,026		151,575	113,570
Net income	198,043	$ 295,783	204,925	$ 172,515	$ 493,826	377,440
Maximum
Costs and expenses:
Percent of target bonus charges allocated to segments					100.00%
Operating Segments
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	1,031,053		967,714		$ 2,008,163	1,865,229
Costs and expenses:
Operating income	1,031,053		967,714		2,008,163	1,865,229
Corporate and Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	(747,946)		(670,592)		(1,317,099)	(1,350,860)
Costs and expenses:
Cost of services and product development - unallocated	15,286		15,728		18,666	27,536
Selling, general and administrative	680,168		604,911		1,337,258	1,222,815
Depreciation and amortization	46,613		47,664		93,244	96,013
Acquisition and integration charges	1,973		2,289		3,341	4,496
Operating income	$ (747,946)		$ (670,592)		$ (1,317,099)	$ (1,350,860)