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Acquisitions - Additional Information (Detail) - SiriusDecisions, Inc [Member] $ in Millions |  | 3 Months Ended
--- | --- | ---
Jan. 03, 2019 USD ($) Employee | Mar. 31, 2019 USD ($)
Business Acquisition [Line Items] |  |
Percentage of issued and outstanding shares acquired | 100.00% |
Number of employees | Employee | 350 |
Purchase price paid | $ 246.8 |
Acquisition costs recognized |  | $ 1.7

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- Definition Percentage of voting equity interests acquired at the acquisition date in the business combination. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 805 -SubTopic 10 -Section 50 -Paragraph 2 -Subparagraph (c) -URI http://asc.fasb.org/extlink&oid=79982066&loc=d3e1392-128463 + Details
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