Segment Information - Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($) $ in Thousands	1 Months Ended	3 Months Ended				6 Months Ended
	May 31, 2021	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2021	Jun. 30, 2020
Costs and expenses:
Cost of services and product development		$ 350,802		$ 322,551		$ 685,269	$ 663,829
Selling, general and administrative		488,496		494,840		975,751	991,479
Acquisition and integration charges		1,302		2,157		1,942	3,716
Operating income		274,714		99,651		500,126	224,370
Interest expense and other, net		(31,072)		(40,695)		(41,731)	(68,559)
Gain on event cancellation insurance claims	$ 135,500	135,545		0		135,545	0
Less: Provision for income taxes		107,951		3,879		158,604	25,637
Net income		271,236	$ 164,100	55,077	$ 75,097	435,336	130,174
Reportable segments
Costs and expenses:
Operating income		827,503		654,936		$ 1,604,869	1,331,729
Reportable segments | Maximum
Costs and expenses:
Percent of target bonus allocated to segments						100.00%
Corporate and other expenses
Costs and expenses:
Cost of services and product development		10,986		4,352		$ 18,781	3,532
Selling, general and administrative		488,496		494,840		975,751	991,479
Depreciation and amortization		52,005		53,936		108,269	108,632
Acquisition and integration charges		1,302		2,157		1,942	3,716
Operating income		$ (552,789)		$ (555,285)		$ (1,104,743)	$ (1,107,359)