Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2023	Sep. 30, 2022
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	$ 244,417			$ 253,418			$ 935,481	$ 767,787
Costs and expenses:
Cost of services and product development - unallocated	450,841			416,837			1,373,398	1,218,405
Selling, general and administrative	660,527			613,031			1,997,785	1,835,846
Acquisition and integration charges	4,463			1,331			7,804	5,827
Gain from sale of divested operation	0			0			(135,410)	0
Operating income	244,417			253,418			935,481	767,787
Interest expense and other, net	(19,943)			(21,356)			(68,683)	(44,715)
Gain on event cancellation insurance claims	0			0			3,077	0
Less: Provision for income taxes	44,465			58,517			196,040	172,087
Net income	180,009	$ 198,043	$ 295,783	173,545	$ 204,925	$ 172,515	$ 673,835	550,985
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	963,149			925,969			$ 2,971,312	2,791,198
Costs and expenses:
Operating income	963,149			925,969			2,971,312	2,791,198
Corporate and Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	(718,732)			(672,551)			(2,035,831)	(2,023,411)
Costs and expenses:
Cost of services and product development - unallocated	5,206			10,938			23,872	38,474
Selling, general and administrative	660,527			613,031			1,997,785	1,835,846
Depreciation and amortization	48,536			47,251			141,780	143,264
Acquisition and integration charges	4,463			1,331			7,804	5,827
Operating income	$ (718,732)			$ (672,551)			$ (2,035,831)	$ (2,023,411)