Consolidated Statements of Operations - USD ($) shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Revenues:
Total revenues	$ 5,475,846	$ 4,733,962	$ 4,099,403
Costs and expenses:
Cost of services and product development	1,693,771	1,444,093	1,345,024
Selling, general and administrative	2,480,944	2,155,658	2,038,963
Depreciation	93,410	102,802	93,925
Amortization of intangibles	98,536	109,603	125,059
Acquisition and integration charges	9,079	6,055	6,282
Total costs and expenses	4,375,740	3,818,211	3,609,253
Operating income	1,100,106	915,751	490,150
Interest income	4,880	1,893	2,087
Interest expense	(126,203)	(118,513)	(115,636)
Gain on event cancellation insurance claims	0	152,310	0
Loss on extinguishment of debt	0	0	(44,814)
Other income (expense), net	48,412	18,429	(5,654)
Income before income taxes	1,027,195	969,870	326,133
Provision for income taxes	219,396	176,310	59,388
Net income	$ 807,799	$ 793,560	$ 266,745
Net income per share:
Basic (in dollars per share)	$ 10.08	$ 9.33	$ 2.99
Diluted (in dollars per share)	$ 9.96	$ 9.21	$ 2.96
Weighted average shares outstanding:
Basic (in shares)	80,178	85,026	89,315
Diluted (in shares)	81,067	86,177	90,017
Research
Revenues:
Total revenues	$ 4,604,791	$ 4,101,392	$ 3,602,892
Conferences
Revenues:
Total revenues	389,273	214,449	120,140
Consulting
Revenues:
Total revenues	$ 481,782	$ 418,121	$ 376,371