Retirement Plans, Postretirement and Postemployment Benefits - Schedule of Fair Values of Pension Plan Assets by Asset Class and Fair Value Hierarchy Level (Detail) - USD ($) $ in Millions	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	$ 1,200.3	$ 1,037.9
Quoted Prices In Active Markets For Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	3.9	3.5
Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	1,196.4	1,034.4
Mid-sized to Large Cap
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	351.6	302.3
Mid-sized to Large Cap | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	351.6	302.3
Small Cap, International and Emerging Growth Funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	354.5	328.4
Small Cap, International and Emerging Growth Funds | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	354.5	328.4
Debt Securities
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	319.3	248.2
Debt Securities | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	319.3	248.2
Real Estate
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	86.6	80.4
Real Estate | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	86.6	80.4
Private Infrastructure
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	78.5	50.2
Private Infrastructure | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	78.5	50.2
Hedge Funds
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	5.9	24.9
Hedge Funds | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	5.9	24.9
Cash Equivalents
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	3.9	3.5
Cash Equivalents | Quoted Prices In Active Markets For Identical Assets (Level 1)
Defined Benefit Plan Disclosure [Line Items]
Fair values of pension plan assets	$ 3.9	$ 3.5