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Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,524,072	$ 1,484,306	$ 4,744,656	$ 4,552,292
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,362,968	1,307,428	4,090,501	3,892,493
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	161,104	176,878	654,155	659,799
Insights
Disaggregation of Revenue [Line Items]
Total revenues	1,270,724	1,209,524	3,789,798	3,582,238
Insights | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,268,460	1,205,568	3,781,197	3,573,963
Insights | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	2,264	3,956	8,601	8,275
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	74,554	75,776	358,558	331,929
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	74,554	75,776	358,558	331,929
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	123,573	127,622	418,873	405,291
Consulting | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	94,043	101,246	308,077	316,417
Consulting | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	29,530	26,376	110,796	88,874
Other
Disaggregation of Revenue [Line Items]
Total revenues	55,221	71,384	177,427	232,834
Other | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	465	614	1,227	2,113
Other | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 54,756	$ 70,770	$ 176,200	$ 230,721

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