Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,686,454	$ 1,595,060	$ 3,220,584	$ 3,067,986
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,370,793	1,294,210	2,727,533	2,585,065
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	315,661	300,850	493,051	482,921
Insights
Disaggregation of Revenue [Line Items]
Total revenues	1,319,453	1,265,992	2,641,280	2,534,164
Insights | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,260,911	1,187,626	2,513,499	2,369,894
Insights | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	58,542	78,366	127,781	164,270
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	211,407	186,084	284,004	256,153
Conferences | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0	0
Conferences | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	211,407	186,084	284,004	256,153
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	155,594	142,984	295,300	277,669
Consulting | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	109,882	106,584	214,034	215,171
Consulting | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 45,712	$ 36,400	$ 81,266	$ 62,498