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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