Quarterly report pursuant to Section 13 or 15(d)

Significant Accounting Policies - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash for Balance Sheets and Cash Flows (Detail)

v3.20.2
Significant Accounting Policies - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash for Balance Sheets and Cash Flows (Detail) - USD ($)
$ in Millions
Sep. 30, 2020
Dec. 31, 2019
Sep. 30, 2019
Dec. 31, 2018
Cash, Cash Equivalents and Restricted Cash [Line Items]        
Cash and cash equivalents $ 1,034.6 $ 839.4    
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows 1,042.9 847.5 $ 723.2 $ 1,215.0
Prepaid expenses and other current assets [Member]        
Cash, Cash Equivalents and Restricted Cash [Line Items]        
Restricted cash 2.5 2.5    
Other Assets [Member]        
Cash, Cash Equivalents and Restricted Cash [Line Items]        
Restricted cash $ 5.8 $ 5.6