Goodwill and Intangible Assets - Changes to the Carrying Amount of Goodwill by Segment (Details) - USD ($)	6 Months Ended
	Jun. 30, 2025	Dec. 31, 2024
Goodwill [Roll Forward]
Beginning balance	$ 2,930,205,000
Foreign currency translation impact	7,501,000
Ending balance	2,937,706,000
Goodwill, accumulated impairment losses	0	$ 0
Insights
Goodwill [Roll Forward]
Beginning balance	2,650,981,000
Foreign currency translation impact	6,405,000
Ending balance	2,657,386,000
Conferences
Goodwill [Roll Forward]
Beginning balance	183,920,000
Foreign currency translation impact	105,000
Ending balance	184,025,000
Consulting
Goodwill [Roll Forward]
Beginning balance	95,304,000
Foreign currency translation impact	991,000
Ending balance	$ 96,295,000