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Defined Benefit Plans - Reconciliation of Level Three Measurements (Detail) - USD ($)
$ in Millions
12 Months Ended
Dec. 31, 2022
Dec. 31, 2021
Defined Benefit Plan Disclosure [Line Items]    
Beginning balance $ 649.8  
Ending balance 482.5 $ 649.8
Group annuity/insurance contracts (Level 3)    
Defined Benefit Plan Disclosure [Line Items]    
Beginning balance 25.5 24.8
Actual return on assets related to assets still held 0.5 0.7
Ending balance $ 26.0 $ 25.5