Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2024	Jun. 30, 2024	Mar. 31, 2024	Sep. 30, 2023	Jun. 30, 2023	Mar. 31, 2023	Sep. 30, 2024	Sep. 30, 2023
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	$ 245,824			$ 244,417			$ 838,492	$ 935,481
Costs and expenses:
Cost of services and product development - unallocated	475,342			450,841			1,448,097	1,373,398
Selling, general and administrative	711,729			660,527			2,113,633	1,997,785
Acquisition and integration charges	159			4,463			977	7,804
Gain from sale of divested operation	0			0			0	135,410
Operating income	245,824			244,417			838,492	935,481
Interest expense and other, net	(18,952)			(19,943)			(52,766)	(68,683)
Gain on event cancellation insurance claims	300,000			0			300,000	3,077
Less: Provision for income taxes	111,823			44,465			230,584	196,040
Net income	415,049	$ 229,548	$ 210,545	180,009	$ 198,043	$ 295,783	$ 855,142	673,835
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	1,015,432			963,149			$ 3,132,495	2,971,312
Costs and expenses:
Operating income	1,015,432			963,149			3,132,495	2,971,312
Corporate and Reconciling Items
Segment Reporting, Reconciling Item for Operating Profit (Loss) from Segment to Consolidated [Line Items]
Total segment gross contribution	(769,608)			(718,732)			(2,294,003)	(2,035,831)
Costs and expenses:
Cost of services and product development - unallocated	6,468			5,206			28,300	23,872
Selling, general and administrative	711,729			660,527			2,113,633	1,997,785
Depreciation and amortization	51,252			48,536			151,093	141,780
Acquisition and integration charges	159			4,463			977	7,804
Operating income	$ (769,608)			$ (718,732)			$ (2,294,003)	$ (2,035,831)