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Derivative Financial Instruments - Information about Fair Values of Derivative Instruments in Consolidated Balance Sheet (Parenthetical) (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Offsetting [Abstract]    
Reduction in estimated fair value of interest rate contracts in asset position $ (5.6) $ (43.3)
Reduction in estimated fair value of interest rate contracts in liability position $ (806.5) $ (281.3)