Annual report pursuant to Section 13 and 15(d)

Basis of Presentation - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash for Balance Sheets and Cash Flows (Detail)

v3.20.4
Basis of Presentation - Summary of Reconciliation of Cash, Cash Equivalents and Restricted Cash for Balance Sheets and Cash Flows (Detail) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Cash, Cash Equivalents and Restricted Cash [Line Items]        
Cash and cash equivalents $ 1,045.4 $ 839.4    
Total cash, cash equivalents, and restricted cash shown in the statement of cash flows 1,054.0 847.5 $ 1,215.0 $ 1,295.5
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 $ 6.1 $ 5.6