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Goodwill and Intangible Assets - Changes to the Carrying Amount of Goodwill by Segment (Details) - USD ($) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020
Goodwill [Roll Forward] |  |
Beginning Balance | $ 2,945,547 | $ 2,937,726
Additions due to acquisition | 11,486 |
Foreign currency translation impact and other | (5,716) | 7,821
Ending Balance | 2,951,317 | 2,945,547
Research |  |
Goodwill [Roll Forward] |  |
Beginning Balance | 2,664,732 | 2,651,060
Additions due to acquisition | 11,486 |
Foreign currency translation impact and other | (5,284) | 13,672
Ending Balance | 2,670,934 | 2,664,732
Conferences |  |
Goodwill [Roll Forward] |  |
Beginning Balance | 184,091 | 189,641
Additions due to acquisition | 0 |
Foreign currency translation impact and other | (70) | (5,550)
Ending Balance | 184,021 | 184,091
Consulting |  |
Goodwill [Roll Forward] |  |
Beginning Balance | 96,724 | 97,025
Additions due to acquisition | 0 |
Foreign currency translation impact and other | (362) | (301)
Ending Balance | $ 96,362 | $ 96,724

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- Definition Amount after accumulated impairment loss of an asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(10)(1)) -URI http://asc.fasb.org/extlink&oid=120398452&loc=d3e534808-122878 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 5 -URI http://asc.fasb.org/extlink&oid=120320667&loc=SL49117168-202975 Reference 3: http://www.xbrl.org/2003/role/exampleRef -Publisher FASB -Name Accounting Standards Codification -Topic 852 -SubTopic 10 -Section 55 -Paragraph 10 -URI http://asc.fasb.org/extlink&oid=84165509&loc=d3e56426-112766 Reference 4: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 45 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=99380562&loc=d3e13770-109266 + Details
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- Definition Amount of increase in asset representing future economic benefits arising from other assets acquired in a business combination that are not individually identified and separately recognized resulting from a business combination. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 350 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=121556970&loc=d3e13816-109267 + Details
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