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Employee Benefits - Plan Assets (Details) - USD ($) $ in Millions | Dec. 31, 2022 | Dec. 31, 2021 | Dec. 31, 2020
--- | --- | --- | ---
Pension Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | $ 2,628.0 | $ 3,328.9 | $ 3,225.0
Pension Plan | Level 1, 2, and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 1,367.4 | 1,918.0 |
Pension Plan | Level 1, 2, and 3 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 231.5 | 417.1 |
Pension Plan | Level 1, 2, and 3 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 202.2 | 313.7 |
Pension Plan | Level 1, 2, and 3 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 838.7 | 1,068.7 |
Pension Plan | Level 1, 2, and 3 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 95.0 | 118.5 |
Pension Plan | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 433.7 | 730.8 |
Pension Plan | Level 1 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 231.5 | 417.1 |
Pension Plan | Level 1 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 202.2 | 313.7 |
Pension Plan | Level 1 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 1 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 933.7 | 1,187.2 |
Pension Plan | Level 2 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 2 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 2 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 838.7 | 1,068.7 |
Pension Plan | Level 2 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 95.0 | 118.5 |
Pension Plan | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 3 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 3 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 3 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Level 3 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
Pension Plan | Investments measured at net asset value per share | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 466.0 | 659.2 |
Pension Plan | Investments measured at net asset value per share | Fixed income securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 101.0 | 127.7 |
Pension Plan | Investments measured at net asset value per share | Other investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 693.6 | 624.0 |
OPEB Plan |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 835.3 | 1,000.2 | $ 951.4
OPEB Plan | Level 1, 2, and 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 464.7 | 617.4 |
OPEB Plan | Level 1, 2, and 3 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 92.5 | 135.4 |
OPEB Plan | Level 1, 2, and 3 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 83.9 | 109.1 |
OPEB Plan | Level 1, 2, and 3 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 275.1 | 357.3 |
OPEB Plan | Level 1, 2, and 3 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 13.2 | 15.6 |
OPEB Plan | Level 1 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 306.2 | 409.5 |
OPEB Plan | Level 1 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 92.5 | 135.4 |
OPEB Plan | Level 1 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 83.9 | 109.1 |
OPEB Plan | Level 1 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 129.8 | 165.0 |
OPEB Plan | Level 1 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 2 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 158.5 | 207.9 |
OPEB Plan | Level 2 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 2 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 2 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 145.3 | 192.3 |
OPEB Plan | Level 2 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 13.2 | 15.6 |
OPEB Plan | Level 3 |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 3 | United States equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 3 | International equity |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 3 | United States bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Level 3 | International bonds |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 0.0 | 0.0 |
OPEB Plan | Investments measured at net asset value per share | Equity securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 186.6 | 224.5 |
OPEB Plan | Investments measured at net asset value per share | Fixed income securities |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | 65.5 | 112.3 |
OPEB Plan | Investments measured at net asset value per share | Other investments |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |
Fair Value of Plan Assets | $ 118.5 | $ 46.0 |

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