XML 101 R78.htm IDEA: XBRL DOCUMENT v3.20.4
Retirement Plans - Summary of Projected Benefit Obligations in Excess of Plan Assets (Detail) - Pension Benefits - USD ($)
$ in Millions
Dec. 31, 2020
Dec. 31, 2019
Defined Benefit Plan Disclosure [Line Items]    
Projected benefit obligation $ 872.0 $ 819.7
Fair value of plan assets $ 780.0 $ 705.5