Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2024	Mar. 31, 2024	Jun. 30, 2023	Mar. 31, 2023	Jun. 30, 2024	Jun. 30, 2023
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	$ 318,783		$ 283,107		$ 592,668	$ 691,064
Costs and expenses:
Cost of services and product development - unallocated	513,314		487,418		972,755	922,557
Selling, general and administrative	712,071		680,168		1,401,904	1,337,258
Acquisition and integration charges	358		1,973		818	3,341
Gain from sale of divested operation	0		(3,906)		0	135,410
Operating income	318,783		283,107		592,668	691,064
Interest expense and other, net	(19,486)		(18,983)		(33,814)	(48,740)
Gain on event cancellation insurance claims	0		0		0	3,077
Less: Provision for income taxes	69,749		66,081		118,761	151,575
Net income	229,548	$ 210,545	198,043	$ 295,783	$ 440,093	493,826
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	1,094,952		1,031,053		$ 2,117,063	2,008,163
Costs and expenses:
Operating income	1,094,952		1,031,053		2,117,063	2,008,163
Corporate and Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	(776,169)		(747,946)		(1,524,395)	(1,317,099)
Costs and expenses:
Cost of services and product development - unallocated	13,206		15,286		21,832	18,666
Selling, general and administrative	712,071		680,168		1,401,904	1,337,258
Depreciation and amortization	50,534		46,613		99,841	93,244
Acquisition and integration charges	358		1,973		818	3,341
Operating income	$ (776,169)		$ (747,946)		$ (1,524,395)	$ (1,317,099)