Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (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
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,294,210	1,217,249	2,585,065	2,424,052
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	300,850	285,936	482,921	488,002
Research
Disaggregation of Revenue [Line Items]
Total revenues	1,265,992	1,207,885	2,534,164	2,425,076
Research | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	1,187,626	1,113,328	2,369,894	2,223,124
Research | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	78,366	94,557	164,270	201,952
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	186,084	168,897	256,153	233,539
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	186,084	168,897	256,153	233,539
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	142,984	126,403	277,669	253,439
Consulting | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	106,584	103,921	215,171	200,928
Consulting | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 36,400	$ 22,482	$ 62,498	$ 52,511