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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

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