Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Disaggregation of Revenue [Line Items]
Total revenues	$ 6,497,226	$ 6,267,411	$ 5,906,956
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	5,462,404	5,241,103	4,906,792
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	1,034,822	1,026,308	1,000,164
Insights
Disaggregation of Revenue [Line Items]
Total revenues	5,072,570	4,829,051	4,516,035
Insights | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	5,062,390	4,818,254	4,502,783
Insights | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	10,180	10,797	13,252
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	644,743	583,224	505,164
Conferences | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Conferences | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	644,743	583,224	505,164
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	552,499	558,537	514,746
Consulting | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	398,551	420,160	400,171
Consulting | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	153,948	138,377	114,575
Other
Disaggregation of Revenue [Line Items]
Total revenues	227,414	296,599	371,011
Other | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,463	2,689	3,838
Other | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 225,951	$ 293,910	$ 367,173