Revenue and Related Matters - Timing Of Revenue Recognition Liabilities per Segment (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022	Dec. 31, 2021
Disaggregation of Revenue [Line Items]
Total revenues	$ 5,906,956	$ 5,475,846	$ 4,733,962
Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	4,906,792	4,560,809	4,075,639
Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	1,000,164	915,037	658,323
Research
Disaggregation of Revenue [Line Items]
Total revenues	4,887,046	4,604,791	4,101,392
Research | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	4,506,621	4,182,747	3,740,694
Research | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	380,425	422,044	360,698
Conferences
Disaggregation of Revenue [Line Items]
Total revenues	505,164	389,273	214,449
Conferences | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	0	0	0
Conferences | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	505,164	389,273	214,449
Consulting
Disaggregation of Revenue [Line Items]
Total revenues	514,746	481,782	418,121
Consulting | Transferred over time
Disaggregation of Revenue [Line Items]
Total revenues	400,171	378,062	334,945
Consulting | Transferred at a point in time
Disaggregation of Revenue [Line Items]
Total revenues	$ 114,575	$ 103,720	$ 83,176