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Revenue and Related Matters - Disaggregation of Revenue by Geographic Area (Details) - USD ($) $ in Thousands | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2025 | Sep. 30, 2024 | Sep. 30, 2025 | Sep. 30, 2024
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | $ 1,524,072 | $ 1,484,306 | $ 4,744,656 | $ 4,552,292
United States and Canada |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 907,568 | 923,834 | 2,957,819 | 2,940,465
Europe, Middle East and Africa |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 418,727 | 369,039 | 1,209,780 | 1,072,472
Other International |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 197,777 | 191,433 | 577,057 | 539,355
Insights |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 1,270,724 | 1,209,524 | 3,789,798 | 3,582,238
Insights | United States and Canada |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 770,945 | 777,405 | 2,342,406 | 2,313,152
Insights | Europe, Middle East and Africa |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 340,492 | 288,649 | 977,139 | 841,781
Insights | Other International |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 159,287 | 143,470 | 470,253 | 427,305
Conferences |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 74,554 | 75,776 | 358,558 | 331,929
Conferences | United States and Canada |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 11,433 | 8,191 | 205,302 | 187,400
Conferences | Europe, Middle East and Africa |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 39,356 | 40,486 | 103,793 | 97,443
Conferences | Other International |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 23,765 | 27,099 | 49,463 | 47,086
Consulting |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 123,573 | 127,622 | 418,873 | 405,291
Consulting | United States and Canada |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 78,299 | 79,448 | 261,042 | 248,930
Consulting | Europe, Middle East and Africa |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 32,987 | 30,637 | 108,086 | 101,920
Consulting | Other International |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 12,287 | 17,537 | 49,745 | 54,441
Other |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 55,221 | 71,384 | 177,427 | 232,834
Other | United States and Canada |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 46,891 | 58,790 | 149,069 | 190,983
Other | Europe, Middle East and Africa |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | 5,892 | 9,267 | 20,762 | 31,328
Other | Other International |  |  |  |
Disaggregation of Revenue [Line Items] |  |  |  |
Total revenues | $ 2,438 | $ 3,327 | $ 7,596 | $ 10,523

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