Revenue and Related Matters - Disaggregation of Revenue by Geographic Area (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,595,060	$ 1,503,185	$ 3,067,986	$ 2,912,054
United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	1,054,781	1,012,380	2,016,631	1,947,529
Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	368,960	330,923	703,433	641,725
Other International
Disaggregation of Revenue [Line Items]
Total revenues	171,319	159,882	347,922	322,800
Research
Disaggregation of Revenue [Line Items]
Total revenues	1,265,992	1,207,885	2,534,164	2,425,076
Research | United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	832,719	812,724	1,667,940	1,622,123
Research | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	287,650	258,255	575,193	526,912
Research | Other International
Disaggregation of Revenue [Line Items]
Total revenues	145,623	136,906	291,031	276,041
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	186,084	168,897	256,153	233,539
Conferences | United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	131,119	123,243	179,209	172,018
Conferences | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	46,629	38,803	56,957	48,010
Conferences | Other International
Disaggregation of Revenue [Line Items]
Total revenues	8,336	6,851	19,987	13,511
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	142,984	126,403	277,669	253,439
Consulting | United States and Canada
Disaggregation of Revenue [Line Items]
Total revenues	90,943	76,413	169,482	153,388
Consulting | Europe, Middle East and Africa
Disaggregation of Revenue [Line Items]
Total revenues	34,681	33,865	71,283	66,803
Consulting | Other International
Disaggregation of Revenue [Line Items]
Total revenues	$ 17,360	$ 16,125	$ 36,904	$ 33,248