Condensed Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022
Revenues:
Total revenues	$ 1,408,784	$ 1,331,868	$ 4,320,838	$ 3,971,129
Costs and expenses:
Cost of services and product development	450,841	416,837	1,373,398	1,218,405
Selling, general and administrative	660,527	613,031	1,997,785	1,835,846
Depreciation	24,547	22,882	72,155	68,993
Amortization of intangibles	23,989	24,369	69,625	74,271
Acquisition and integration charges	4,463	1,331	7,804	5,827
Gain from sale of divested operation	0	0	(135,410)	0
Total costs and expenses	1,164,367	1,078,450	3,385,357	3,203,342
Operating income	244,417	253,418	935,481	767,787
Interest expense, net	(21,820)	(30,286)	(73,769)	(91,399)
Gain on event cancellation insurance claims	0	0	3,077	0
Other income, net	1,877	8,930	5,086	46,684
Income before income taxes	224,474	232,062	869,875	723,072
Provision for income taxes	44,465	58,517	196,040	172,087
Net income	$ 180,009	$ 173,545	$ 673,835	$ 550,985
Net income per share:
Basic (in dollars per share)	$ 2.28	$ 2.19	$ 8.51	$ 6.84
Diluted (in dollars per share)	$ 2.26	$ 2.17	$ 8.44	$ 6.77
Weighted average shares outstanding:
Basic (in shares)	78,923	79,259	79,220	80,516
Diluted (in shares)	79,520	80,059	79,862	81,373
Research
Revenues:
Total revenues	$ 1,218,739	$ 1,147,823	$ 3,643,815	$ 3,426,532
Conferences
Revenues:
Total revenues	57,200	77,031	290,739	200,910
Consulting
Revenues:
Total revenues	$ 132,845	$ 107,014	$ 386,284	$ 343,687