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Pension and Post-Employment Benefits - Fair Value of Pension Assets (Detail) - USD ($) $ in Millions | Dec. 31, 2018 | Dec. 31, 2017 | Dec. 31, 2016
--- | --- | --- | ---
Fair value of pension assets |  |  |
Total plan assets | $ 95.9 | $ 116.0 |
United Kingdom Plan [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 701.0 | 762.4 |
Cash | 38.1 | 75.0 |
Total plan assets | 739.1 | 837.4 | $ 758.2
United Kingdom Plan [Member] | Debt Securities Issued by Non-U.S. Government and Government Agencies [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 67.2 | 86.0 |
United Kingdom Plan [Member] | Corporate Debt Securities [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 406.4 | 426.8 |
United Kingdom Plan [Member] | Equity Securities Held for Proprietary Investment Purposes [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value |  | 0.1 |
United Kingdom Plan [Member] | Real Estate [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 31.4 | 34.4 |
United Kingdom Plan [Member] | Insurance Contracts [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 142.5 | 162.8 |
United Kingdom Plan [Member] | Investments Measured At Net Asset Value [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 53.0 | 52.3 |
United Kingdom Plan [Member] | Other Financial Derivatives [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 0.5 |  |
United Kingdom Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 98.6 | 315.0 |
Cash | 38.1 | 75.0 |
Total plan assets | 136.7 | 390.0 |
United Kingdom Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Debt Securities Issued by Non-U.S. Government and Government Agencies [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 67.2 | 86.0 |
United Kingdom Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Corporate Debt Securities [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value |  | 194.5 |
United Kingdom Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Equity Securities Held for Proprietary Investment Purposes [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value |  | 0.1 |
United Kingdom Plan [Member] | Quoted Prices in Active Markets for Identical Assets (Level 1) [Member] | Real Estate [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 31.4 | 34.4 |
United Kingdom Plan [Member] | Significant Other Observable Inputs (Level 2) [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 406.9 | 232.3 |
Total plan assets | 406.9 | 232.3 |
United Kingdom Plan [Member] | Significant Other Observable Inputs (Level 2) [Member] | Corporate Debt Securities [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 406.4 | 232.3 |
United Kingdom Plan [Member] | Significant Other Observable Inputs (Level 2) [Member] | Other Financial Derivatives [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 0.5 |  |
United Kingdom Plan [Member] | Significant Unobservable Inputs (Level 3) [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | 142.5 | 162.8 |
Total plan assets | 142.5 | 162.8 |
United Kingdom Plan [Member] | Significant Unobservable Inputs (Level 3) [Member] | Insurance Contracts [Member] |  |  |
Fair value of pension assets |  |  |
Total assets at fair value | $ 142.5 | $ 162.8 |

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