Revenue and Related Matters - Disaggregation of Revenue by Geographic Area (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
United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	961,850	935,149
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	334,473	310,802
Other International
Disaggregation of Revenue [Line Items]
Total revenues	176,603	162,918
Research
Disaggregation of Revenue [Line Items]
Total revenues	1,268,172	1,217,191
Research | United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	835,221	809,399
Research | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	287,543	268,657
Research | Other International
Disaggregation of Revenue [Line Items]
Total revenues	145,408	139,135
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	70,069	64,642
Conferences | United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	48,090	48,775
Conferences | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	10,328	9,207
Conferences | Other International
Disaggregation of Revenue [Line Items]
Total revenues	11,651	6,660
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	134,685	127,036
Consulting | United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	78,539	76,975
Consulting | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	36,602	32,938
Consulting | Other International
Disaggregation of Revenue [Line Items]
Total revenues	$ 19,544	$ 17,123