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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 $ 460.0  
Total contribution to defined contribution plans 47.0 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 8.0  
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 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 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 8.0  
Investments Measured at NAV | International real estate      
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]      
Fair value of plan assets 0.0 0.0  
Investments Measured at NAV | Other      
Defined Benefit Plan, Funded (Unfunded) Status of Plan [Abstract]      
Fair value of plan assets 0.0 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 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 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 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 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 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 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 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 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 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 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 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 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 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 2.0 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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 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