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Business Combinations - Additional Information (Details) - USD ($)
$ in Thousands
Jul. 01, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Dec. 31, 2016
Business Acquisition [Line Items]          
Goodwill   $ 290,366 $ 290,366 $ 170,153 $ 6,788
Sustainable Growth Advisers, LP          
Business Acquisition [Line Items]          
Percentage of voting interests acquired 70.00%        
Purchase price, consideration transferred $ 129,500        
Goodwill 120,213        
Intangible assets 62,000        
Goodwill and other intangible assets, amount expected to be tax deductible $ 127,500        
SGIA, LLC | Sustainable Growth Advisers, LP | Sustainable Growth Advisers, LP          
Business Acquisition [Line Items]          
Percentage of membership interests 100.00%