Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2022	Sep. 30, 2021	Sep. 30, 2022	Sep. 30, 2021
Disaggregation of Revenue [Line Items]
Total revenues	$ 1,331,868	$ 1,156,282	$ 3,971,129	$ 3,427,639
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,135,741	1,021,744	3,391,052	3,002,916
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	196,127	134,538	580,077	424,723
Research
Disaggregation of Revenue [Line Items]
Total revenues	1,147,823	1,037,124	3,426,532	3,020,094
Research | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,045,425	944,206	3,109,099	2,755,047
Research | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	102,398	92,918	317,433	265,047
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	77,031	24,415	200,910	107,396
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	77,031	24,415	200,910	107,396
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	107,014	94,743	343,687	300,149
Consulting | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	90,316	77,538	281,953	247,869
Consulting | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 16,698	$ 17,205	$ 61,734	$ 52,280