Pension and Other Post-retirement Benefits - Fair Value Measurement of Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019 |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | $ 822.4 | $ 857.3 | |
Non-investment plan assets | 3.5 | 1.5 | |
Total plan assets | 825.9 | 858.8 | |
Short-term investments | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 182.9 | 13.7 | |
Common stocks | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 3.7 | 136.5 | |
Commingled equity funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 132 | |
U.S. Treasury securities | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 52.8 | 44.3 | |
Other fixed income securities | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 551.2 | 229.1 | |
Commingled fixed income funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 119.5 | |
Options | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | (8.1) | |
Mutual funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 26.7 | 105.6 | |
Real estate funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 79.8 | |
Private equity | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 5.1 | 4.9 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 239.4 | 180.8 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | Short-term investments | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 182.9 | 0 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | Common stocks | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 3.7 | 136.5 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | Commingled equity funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | U.S. Treasury securities | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 52.8 | 44.3 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | Other fixed income securities | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | Commingled fixed income funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | Options | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | Mutual funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | Real estate funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Quoted Prices in Active Markets for Identical Contracts (Level 1) | Private equity | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Other Observable Inputs (Level 2) | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 577.9 | 591.8 | |
Significant Other Observable Inputs (Level 2) | Short-term investments | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 13.7 | |
Significant Other Observable Inputs (Level 2) | Common stocks | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Other Observable Inputs (Level 2) | Commingled equity funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 132 | |
Significant Other Observable Inputs (Level 2) | U.S. Treasury securities | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Other Observable Inputs (Level 2) | Other fixed income securities | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 551.2 | 229.1 | |
Significant Other Observable Inputs (Level 2) | Commingled fixed income funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 119.5 | |
Significant Other Observable Inputs (Level 2) | Options | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | (8.1) | |
Significant Other Observable Inputs (Level 2) | Mutual funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 26.7 | 105.6 | |
Significant Other Observable Inputs (Level 2) | Real estate funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Other Observable Inputs (Level 2) | Private equity | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Non- observable Inputs (Level 3) | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 5.1 | 84.7 | $ 90.9 |
Significant Non- observable Inputs (Level 3) | Short-term investments | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Non- observable Inputs (Level 3) | Common stocks | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Non- observable Inputs (Level 3) | Commingled equity funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Non- observable Inputs (Level 3) | U.S. Treasury securities | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Non- observable Inputs (Level 3) | Other fixed income securities | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Non- observable Inputs (Level 3) | Commingled fixed income funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Non- observable Inputs (Level 3) | Options | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Non- observable Inputs (Level 3) | Mutual funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 0 | |
Significant Non- observable Inputs (Level 3) | Real estate funds | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | 0 | 79.8 | 82.3 |
Significant Non- observable Inputs (Level 3) | Private equity | | | |
Defined Benefit Plan Disclosure [Line Items] | | | |
Total fair value of plan asset investments | $ 5.1 | $ 4.9 | $ 8.6 |