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Long-Term Debt (Debt Issuance Costs) - Additional Information (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Dec. 31, 2018
Debt Disclosure [Abstract]      
Debt issuance costs $ 29.8 $ 29.0  
Accumulated amortization 56.0 46.2  
Amortization expenses reported as interest expense $ 9.8 $ 9.7 $ 9.0