XML 73 R52.htm IDEA: XBRL DOCUMENT v3.20.4
Summary of significant accounting policies - Reconciliation of Cash, Cash Equivalents and Restricted Cash (Details) - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Accounting Policies [Abstract]        
Cash and cash equivalents $ 898.5 $ 538.8 $ 605.0  
Restricted cash 8.2 13.0    
Total cash, cash equivalents and restricted cash shown in the consolidated statements of cash flows $ 906.7 $ 551.8 $ 624.1 $ 764.1