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Goodwill - Schedule of Changes in Carrying Amount of Goodwill (Detail)
$ in Millions
6 Months Ended
Jun. 30, 2020
USD ($)
Goodwill And Intangible Assets Disclosure [Abstract]  
Balance at December 31, 2019 $ 421.3
Measurement period adjustment (Note 2) 0.7
Balance at June 30, 2020 $ 422.0