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Employee Benefits - Amounts recognized in the Consolidated Statements of Financial Position (Details) - USD ($) $ in Millions | Dec. 31, 2020 | Dec. 31, 2019
--- | --- | ---
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Prepaid pension | $ 1,280 | $ 1,216
Pension Plan | U.S. |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Prepaid pension | 0 | 0
Accrued benefit liability - current | (52) | (50)
Accrued benefit liability - non-current | (1,052) | (1,076)
Accumulated other comprehensive loss | 1,812 | 1,763
Net amount recognized | 708 | 637
Pension Plan | U.K. |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Prepaid pension | 1,268 | 1,200
Accrued benefit liability - current | (1) | (1)
Accrued benefit liability - non-current | (21) | (19)
Accumulated other comprehensive loss | 1,329 | 1,244
Net amount recognized | 2,575 | 2,424
Pension Plan | Other |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |
Prepaid pension | 0 | 0
Accrued benefit liability - current | (5) | (5)
Accrued benefit liability - non-current | (123) | (117)
Accumulated other comprehensive loss | 514 | 454
Net amount recognized | $ 386 | $ 332

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