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PENSION AND POST-RETIREMENT PLANS - FAIR VALUE (Details) - Pension Benefits - USD ($) $ in Millions | Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021
--- | --- | --- | ---
Pension and Post-retirement Plans |  |  |
Total | $ 227.9 | $ 206.3 | $ 238.9
Fair Value Measurement |  |  |
Pension and Post-retirement Plans |  |  |
Total | 186.3 | 166.4 |
Total plan assets | 227.9 | 206.4 |
Fair Value Measurement | Cash |  |  |
Pension and Post-retirement Plans |  |  |
Total | 6.1 | 8.8 |
Fair Value Measurement | U S large-cap |  |  |
Pension and Post-retirement Plans |  |  |
Total | 82.8 | 69.1 |
Fair Value Measurement | U S mid and small-cap |  |  |
Pension and Post-retirement Plans |  |  |
Total | 46.0 | 41.5 |
Fair Value Measurement | International large-cap |  |  |
Pension and Post-retirement Plans |  |  |
Total | 7.1 | 6.2 |
Fair Value Measurement | U S Treasuries |  |  |
Pension and Post-retirement Plans |  |  |
Total | 19.2 | 17.4 |
Fair Value Measurement | Municipal bonds |  |  |
Pension and Post-retirement Plans |  |  |
Total | 0.2 | 0.2 |
Fair Value Measurement | Investment grade U S corporate bonds |  |  |
Pension and Post-retirement Plans |  |  |
Total | 24.7 | 22.8 |
Fair Value Measurement | Convertible Bonds |  |  |
Pension and Post-retirement Plans |  |  |
Total | 0.1 | 0.3 |
Fair Value Measurement | International Fixed Income |  |  |
Pension and Post-retirement Plans |  |  |
Total | 0.1 | 0.1 |
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) |  |  |
Pension and Post-retirement Plans |  |  |
Total | 142.0 | 125.6 |
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | Cash |  |  |
Pension and Post-retirement Plans |  |  |
Total | 6.1 | 8.8 |
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | U S large-cap |  |  |
Pension and Post-retirement Plans |  |  |
Total | 82.8 | 69.1 |
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | U S mid and small-cap |  |  |
Pension and Post-retirement Plans |  |  |
Total | 46.0 | 41.5 |
Fair Value Measurement | Quoted Prices in Active Markets (Level 1) | International large-cap |  |  |
Pension and Post-retirement Plans |  |  |
Total | 7.1 | 6.2 |
Fair Value Measurement | Significant Observable Inputs (Level 2) |  |  |
Pension and Post-retirement Plans |  |  |
Total | 44.3 | 40.8 |
Fair Value Measurement | Significant Observable Inputs (Level 2) | U S Treasuries |  |  |
Pension and Post-retirement Plans |  |  |
Total | 19.2 | 17.4 |
Fair Value Measurement | Significant Observable Inputs (Level 2) | Municipal bonds |  |  |
Pension and Post-retirement Plans |  |  |
Total | 0.2 | 0.2 |
Fair Value Measurement | Significant Observable Inputs (Level 2) | Investment grade U S corporate bonds |  |  |
Pension and Post-retirement Plans |  |  |
Total | 24.7 | 22.8 |
Fair Value Measurement | Significant Observable Inputs (Level 2) | Convertible Bonds |  |  |
Pension and Post-retirement Plans |  |  |
Total | 0.1 | 0.3 |
Fair Value Measurement | Significant Observable Inputs (Level 2) | International Fixed Income |  |  |
Pension and Post-retirement Plans |  |  |
Total | 0.1 | 0.1 |
Fair Value Measurement | Investment measured at NAV |  |  |
Pension and Post-retirement Plans |  |  |
Total | $ 41.6 | $ 40.0 |

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