v3.26.3
Segment Information - Schedule of Reconciliation of Segment Gross Contribution to Net Income (Details) - USD ($)
$ in Thousands
 3 Months Ended 9 Months Ended
Sep. 30, 2026
Sep. 30, 2025
Sep. 30, 2026
Sep. 30, 2025
Segment Reporting [Line Items]        
Revenues $ 1,504,791 $ 1,524,072 $ 4,691,775 $ 4,744,656
Personnel expenses 370,549 387,788 1,114,087 1,178,905
Product and content delivery expenses 43,006 65,961 170,509 242,118
Other expenses 15,601 13,397 46,871 43,792
Gross contribution 1,075,635 1,056,926 3,360,308 3,279,841
Cost of services and product development - unallocated 3,987 7,072 17,892 16,164
Selling, general and administrative 746,842 762,557 2,237,783 2,269,753
Depreciation and amortization 45,081 50,953 135,695 152,452
Goodwill impairment 0 150,000 0 150,000
Gain from sale of divested operation (1,386) 0 (6,785) 0
Interest expenses and other, net 25,430 16,862 73,007 37,189
Income before income taxes 255,681 69,482 902,716 654,283
Insights        
Segment Reporting [Line Items]        
Revenues 1,292,434 1,270,724 3,876,499 3,789,798
Conferences        
Segment Reporting [Line Items]        
Revenues 86,003 74,554 408,485 358,558
Consulting        
Segment Reporting [Line Items]        
Revenues 126,354 123,573 387,399 418,873
Other        
Segment Reporting [Line Items]        
Revenues   55,221 $ 19,392 $ 177,427
Maximum        
Segment Reporting [Line Items]        
Percent of target bonus charges allocated to segments     100.00% 100.00%
Operating Segments | Insights        
Segment Reporting [Line Items]        
Revenues 1,292,434 1,270,724 $ 3,876,499 $ 3,789,798
Personnel expenses 274,566 282,516 822,194 850,941
Product and content delivery expenses 7,282 8,102 18,142 19,429
Other expenses 7,667 5,783 22,354 18,426
Gross contribution 1,002,919 974,323 3,013,809 2,901,002
Operating Segments | Conferences        
Segment Reporting [Line Items]        
Revenues 86,003 74,554 408,485 358,558
Personnel expenses 19,757 18,389 57,015 55,015
Product and content delivery expenses 32,097 25,533 132,499 114,901
Other expenses 4,168 3,320 13,359 12,560
Gross contribution 29,981 27,312 205,612 176,082
Operating Segments | Consulting        
Segment Reporting [Line Items]        
Revenues 126,354 123,573 387,399 418,873
Personnel expenses 76,226 81,040 232,668 246,644
Product and content delivery expenses 3,627 3,588 10,393 10,902
Other expenses 3,766 3,723 11,028 11,158
Gross contribution $ 42,735 35,222 133,310 150,169
Operating Segments | Other        
Segment Reporting [Line Items]        
Revenues   55,221 19,392 177,427
Personnel expenses   5,843 2,210 26,305
Product and content delivery expenses   28,738 9,475 96,886
Other expenses   571 130 1,648
Gross contribution   $ 20,069 $ 7,577 $ 52,588