Employee Benefits - Postretirement Health Care Plan Status (Detail) - Other Postretirement Plan - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
---|---|---|---|
Defined Benefit Plan Disclosure [Line Items] | |||
Net Postretirement Benefit Obligation | $ 15.7 | $ 28.8 | $ 28.1 |
Retirees and Dependents | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Net Postretirement Benefit Obligation | 13.2 | 25.2 | |
Actives Eligible for Benefits | |||
Defined Benefit Plan Disclosure [Line Items] | |||
Net Postretirement Benefit Obligation | $ 2.5 | $ 3.6 |