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Income Taxes - Roll-forward of Unrecognized Tax Benefits and Associated Accrued Interest and Penalties (Detail) - USD ($)
$ in Millions
 6 Months Ended
Jun. 30, 2023
Dec. 31, 2022
Income Tax Contingency [Line Items]    
Opening balance at January 1 $ 13.4  
Net change for tax positions of prior periods 0.6  
Closing balance at June 30 14.0  
Current 0.0  
Non-current 14.0 $ 13.4
Interest and Penalties [Member]    
Income Tax Contingency [Line Items]    
Opening balance at January 1 3.2  
Net change for tax positions of prior periods 0.4  
Closing balance at June 30 3.6  
Current 0.0  
Non-current 3.6  
Unrecognized Tax Benefits [Member]    
Income Tax Contingency [Line Items]    
Opening balance at January 1 10.2  
Net change for tax positions of prior periods 0.2  
Closing balance at June 30 10.4  
Current 0.0  
Non-current $ 10.4