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Summary of Significant Accounting Policies - Additional Information (Detail) - USD ($)
$ in Millions
 3 Months Ended
Mar. 16, 2030
Mar. 05, 2021
Mar. 31, 2021
Mar. 31, 2020
Dec. 31, 2020
Significant Accounting Policies [Line Items]          
Amortization expense for the deferred costs     $ 11.0 $ 9.0  
ASU 2019-12 [Member]          
Significant Accounting Policies [Line Items]          
Change in Accounting Principle, Accounting Standards Update, Adoption Date     Jan. 31, 2021    
Change in Accounting Principle, Accounting Standards Update, Adopted [true false]     true    
Change in Accounting Principle, Accounting Standards Update, Immaterial Effect [true false]     true    
Other Assets [Member]          
Significant Accounting Policies [Line Items]          
Deferred costs     $ 129.1   $ 132.9
Convertible Senior Notes [Member]          
Significant Accounting Policies [Line Items]          
Debt instrument principal amount $ 575.0 $ 500.0 $ 575.0    
Debt instrument percentage of aggregate principal amount 0.25% 0.25% 0.25%    
Debt instrument maturity year 2026 2026      
Debt instrument additional aggregate principal amount $ 75.0   $ 75.0    
Net proceeds from deducting initial purchase discounts and other debt issuance costs   $ 561.8 $ 561.8