Goodwill and Intangible Assets - Changes to Carrying Amount of Goodwill by Reporting Unit (Details)	3 Months Ended	9 Months Ended
	Sep. 30, 2022 USD ($)	Sep. 30, 2022 USD ($)
Goodwill [Line Items]
Goodwill impairment	$ 0
Goodwill [Roll Forward]
Beginning balance		$ 2,951,317,000
Foreign currency translation impact		(15,177,000)
Ending balance	2,936,140,000	2,936,140,000
Goodwill, accumulated impairment losses	0	0
Research
Goodwill [Roll Forward]
Beginning balance		2,670,934,000
Foreign currency translation impact		(12,751,000)
Ending balance	2,658,183,000	2,658,183,000
Conferences
Goodwill [Roll Forward]
Beginning balance		184,021,000
Foreign currency translation impact		(148,000)
Ending balance	183,873,000	183,873,000
Consulting
Goodwill [Roll Forward]
Beginning balance		96,362,000
Foreign currency translation impact		(2,278,000)
Ending balance	$ 94,084,000	$ 94,084,000