Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2024	Mar. 31, 2023
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,472,926	$ 1,408,869
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,290,855	1,206,802
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	182,071	202,067
Research
Disaggregation of Revenue [Line Items]
Total revenues	1,268,172	1,217,191
Research | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,182,268	1,109,796
Research | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	85,904	107,395
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	70,069	64,642
Conferences | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	0	0
Conferences | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	70,069	64,642
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	134,685	127,036
Consulting | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	108,587	97,006
Consulting | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 26,098	$ 30,030