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Basis of Presentation - Additional Information (Details) - USD ($)
$ in Millions
3 Months Ended 6 Months Ended
Jun. 30, 2019
Jun. 30, 2018
Jun. 30, 2019
Jun. 30, 2018
Organization Consolidation And Presentation Of Financial Statements [Abstract]        
Research and development expenses $ 22.4 $ 21.8 $ 43.1 $ 41.3