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Employee Benefits - Additional Information (Details) £ in Millions, $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Jun. 30, 2020 USD ($) | Jun. 30, 2020 GBP (£) | Sep. 30, 2020 USD ($) | Sep. 30, 2019 USD ($)
U.K. |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Non-cash settlement charge | $ 2 | £ 2 | $ 2 | $ 0
Expected future employer cash contribution |  |  | 5 |
Other |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Non-cash settlement charge |  |  | 0 | 0
Expected future employer cash contribution |  |  | 19 |
U.S. |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Non-cash settlement charge |  |  | 0 | $ 0
Expected future employer cash contribution |  |  | $ 99 |

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