Benefit Plans - Fair Values of Pension Plan Assets by Asset Category (Details) - USD ($) $ in Millions | 12 Months Ended |
Dec. 31, 2023 | Dec. 31, 2022 | Dec. 31, 2021 |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | $ 443.5 | $ 460 | |
Total contribution to defined contribution plans | 47 | 46.6 | $ 40.6 |
Cash and cash equivalents | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 7.1 | 3.2 | |
Total equity funds | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 65.1 | 90.7 | |
U.S. small-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 3.7 | 3.8 | |
U.S. large-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 19.5 | 22.4 | |
International equity | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 41.9 | 64.5 | |
Fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 326.3 | 322.7 | |
Corporate bonds - international | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 42.7 | 52.2 | |
UK index-linked gilts | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 78.7 | 41.6 | |
U.S. fixed income - government securities | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 43.2 | 33.1 | |
U.S. fixed income - short duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 1.3 | 1.8 | |
U.S. fixed income - intermediate duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 30.9 | 50.3 | |
U.S. fixed income - long corporate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 122.3 | 135.7 | |
Global fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 7.2 | 8 | |
International real estate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 15.4 | 16.6 | |
Other | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 29.6 | 26.8 | |
Investments Measured at NAV | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 259.1 | 286.3 | |
Investments Measured at NAV | Cash and cash equivalents | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Investments Measured at NAV | Total equity funds | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 38.4 | 49.8 | |
Investments Measured at NAV | U.S. small-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 3.7 | 3.8 | |
Investments Measured at NAV | U.S. large-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 17.5 | 18.5 | |
Investments Measured at NAV | International equity | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 17.2 | 27.5 | |
Investments Measured at NAV | Fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 220.7 | 236.5 | |
Investments Measured at NAV | Corporate bonds - international | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 15.8 | 7.6 | |
Investments Measured at NAV | UK index-linked gilts | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Investments Measured at NAV | U.S. fixed income - government securities | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 43.2 | 33.1 | |
Investments Measured at NAV | U.S. fixed income - short duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 1.3 | 1.8 | |
Investments Measured at NAV | U.S. fixed income - intermediate duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 30.9 | 50.3 | |
Investments Measured at NAV | U.S. fixed income - long corporate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 122.3 | 135.7 | |
Investments Measured at NAV | Global fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 7.2 | 8 | |
Investments Measured at NAV | International real estate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Investments Measured at NAV | Other | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 21.3 | 23.3 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Cash and cash equivalents | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 7.1 | 3.2 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Total equity funds | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 14.2 | 20.1 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. small-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. large-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | International equity | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 14.2 | 20.1 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Corporate bonds - international | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | UK index-linked gilts | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. fixed income - government securities | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. fixed income - short duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. fixed income - intermediate duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | U.S. fixed income - long corporate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Global fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | International real estate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Quoted Prices in Active Markets for Identical Assets (Level 1) | Other | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | | | |
Significant Observable Inputs (Level 2) | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 133.5 | 123.6 | |
Significant Observable Inputs (Level 2) | Cash and cash equivalents | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Observable Inputs (Level 2) | Total equity funds | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 12.5 | 20.8 | |
Significant Observable Inputs (Level 2) | U.S. small-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Observable Inputs (Level 2) | U.S. large-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 2 | 3.9 | |
Significant Observable Inputs (Level 2) | International equity | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 10.5 | 16.9 | |
Significant Observable Inputs (Level 2) | Fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 105.6 | 86.2 | |
Significant Observable Inputs (Level 2) | Corporate bonds - international | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 26.9 | 44.6 | |
Significant Observable Inputs (Level 2) | UK index-linked gilts | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 78.7 | 41.6 | |
Significant Observable Inputs (Level 2) | U.S. fixed income - government securities | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Observable Inputs (Level 2) | U.S. fixed income - short duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Observable Inputs (Level 2) | U.S. fixed income - intermediate duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Observable Inputs (Level 2) | U.S. fixed income - long corporate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Observable Inputs (Level 2) | Global fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Observable Inputs (Level 2) | International real estate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 15.4 | 16.6 | |
Significant Observable Inputs (Level 2) | Other | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 29.6 | 26.8 | |
Significant Unobservable Inputs (Level 3) | Cash and cash equivalents | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | Total equity funds | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | U.S. small-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | U.S. large-cap | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | International equity | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | Fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | Corporate bonds - international | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | UK index-linked gilts | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | U.S. fixed income - government securities | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | U.S. fixed income - short duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | U.S. fixed income - intermediate duration | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | U.S. fixed income - long corporate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | Global fixed income | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | International real estate | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | 0 | 0 | |
Significant Unobservable Inputs (Level 3) | Other | | | |
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract] | | | |
Fair value of plan assets | $ 29.6 | $ 26.8 | |