Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Revenues:
Total revenues	$ 6,497,226	$ 6,267,411	$ 5,906,956
Costs and expenses:
Cost of services and product development	2,053,575	2,023,022	1,903,240
Selling, general and administrative	3,067,631	2,884,814	2,701,542
Depreciation	118,015	112,083	98,645
Amortization of intangibles	82,294	90,232	92,458
Acquisition and integration charges	0	973	9,587
Goodwill impairment	150,000	0	0
Gain from sale of divested operation	0	0	(135,410)
Total costs and expenses	5,471,515	5,111,124	4,670,062
Operating income	1,025,711	1,156,287	1,236,894
Interest income	64,716	61,558	38,526
Interest expense	(125,277)	(131,046)	(132,772)
Gain on event cancellation insurance claims	0	300,000	3,077
Other income, net	2,968	575	1,404
Income before income taxes	968,118	1,387,374	1,147,129
Provision for income taxes	238,887	133,659	264,663
Net income	$ 729,231	$ 1,253,715	$ 882,466
Net income per share:
Basic (in dollars per share)	$ 9.68	$ 16.12	$ 11.17
Diluted (in dollars per share)	$ 9.65	$ 16.00	$ 11.08
Weighted average shares outstanding:
Basic (in shares)	75,355	77,785	79,004
Diluted (in shares)	75,605	78,338	79,680
Insights
Revenues:
Total revenues	$ 5,072,570	$ 4,829,051	$ 4,516,035
Conferences
Revenues:
Total revenues	644,743	583,224	505,164
Consulting
Revenues:
Total revenues	552,499	558,537	514,746
Other
Revenues:
Total revenues	$ 227,414	$ 296,599	$ 371,011