Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Revenues:
Total revenues	$ 1,595,060	$ 1,503,185	$ 3,067,986	$ 2,912,054
Costs and expenses:
Cost of services and product development	513,314	487,418	972,755	922,557
Selling, general and administrative	712,071	680,168	1,401,904	1,337,258
Depreciation	27,594	23,712	53,911	47,608
Amortization of intangibles	22,940	22,901	45,930	45,636
Acquisition and integration charges	358	1,973	818	3,341
Gain from sale of divested operation	0	3,906	0	(135,410)
Total costs and expenses	1,276,277	1,220,078	2,475,318	2,220,990
Operating income	318,783	283,107	592,668	691,064
Interest expense, net	(19,990)	(24,558)	(39,209)	(51,949)
Gain on event cancellation insurance claims	0	0	0	3,077
Other income, net	504	5,575	5,395	3,209
Income before income taxes	299,297	264,124	558,854	645,401
Provision for income taxes	69,749	66,081	118,761	151,575
Net income	$ 229,548	$ 198,043	$ 440,093	$ 493,826
Net income per share:
Basic (in dollars per share)	$ 2.95	$ 2.50	$ 5.64	$ 6.22
Diluted (in dollars per share)	$ 2.93	$ 2.48	$ 5.60	$ 6.17
Weighted average shares outstanding:
Basic (in shares)	77,816	79,285	78,078	79,368
Diluted (in shares)	78,288	79,820	78,651	80,015
Research
Revenues:
Total revenues	$ 1,265,992	$ 1,207,885	$ 2,534,164	$ 2,425,076
Conferences
Revenues:
Total revenues	186,084	168,897	256,153	233,539
Consulting
Revenues:
Total revenues	$ 142,984	$ 126,403	$ 277,669	$ 253,439