Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2025	Mar. 31, 2024
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,534,130	$ 1,472,926
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,356,740	1,290,855
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	177,390	182,071
Research
Disaggregation of Revenue [Line Items]
Total revenues	1,321,827	1,268,172
Research | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,252,588	1,182,268
Research | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	69,239	85,904
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	72,597	70,069
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	72,597	70,069
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	139,706	134,685
Consulting | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	104,152	108,587
Consulting | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 35,554	$ 26,098