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Employee Benefits - Summary of Employer Contributions (Details) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2019 | Sep. 30, 2018 | Sep. 30, 2019 | Sep. 30, 2018
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Company’s benefit pension plans | $ 29 | $ 138 | $ 108 | $ 222
U.S. |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Company’s benefit pension plans | 7 | 108 | 30 | 133
U.K. |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Company’s benefit pension plans | 19 | 27 | 65 | 75
Other |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Company’s benefit pension plans | $ 3 | 3 | $ 13 | 14
Qualified Plan [Member] | U.S. |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Company’s benefit pension plans |  | $ 100 |  | $ 100

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