Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2024	Sep. 30, 2023	Sep. 30, 2024	Sep. 30, 2023
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,484,306	$ 1,408,784	$ 4,552,292	$ 4,320,838
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,307,428	1,225,004	3,892,493	3,649,056
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	176,878	183,780	659,799	671,782
Research
Disaggregation of Revenue [Line Items]
Total revenues	1,280,908	1,218,739	3,815,072	3,643,815
Research | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,206,182	1,125,285	3,576,076	3,348,409
Research | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	74,726	93,454	238,996	295,406
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	75,776	57,200	331,929	290,739
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	75,776	57,200	331,929	290,739
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	127,622	132,845	405,291	386,284
Consulting | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	101,246	99,719	316,417	300,647
Consulting | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 26,376	$ 33,126	$ 88,874	$ 85,637