Revenue and Related Matters - Disaggregation of Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,686,454	$ 1,595,060	$ 3,220,584	$ 3,067,986
United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	1,056,422	1,054,781	2,050,251	2,016,631
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	427,908	368,960	791,053	703,433
Other International
Disaggregation of Revenue [Line Items]
Total revenues	202,124	171,319	379,280	347,922
Insights
Disaggregation of Revenue [Line Items]
Total revenues	1,319,453	1,265,992	2,641,280	2,534,164
Insights | United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	826,358	832,719	1,673,639	1,667,940
Insights | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	329,817	287,650	651,517	575,193
Insights | Other International
Disaggregation of Revenue [Line Items]
Total revenues	163,278	145,623	316,124	291,031
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	211,407	186,084	284,004	256,153
Conferences | United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	138,285	131,119	193,869	179,209
Conferences | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	55,295	46,629	64,437	56,957
Conferences | Other International
Disaggregation of Revenue [Line Items]
Total revenues	17,827	8,336	25,698	19,987
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	155,594	142,984	295,300	277,669
Consulting | United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	91,779	90,943	182,743	169,482
Consulting | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	42,796	34,681	75,099	71,283
Consulting | Other International
Disaggregation of Revenue [Line Items]
Total revenues	$ 21,019	$ 17,360	$ 37,458	$ 36,904