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Pension Benefits - Narrative (Details) $ in Millions | 1 Months Ended | 3 Months Ended | 9 Months Ended
--- | --- | --- | ---
Jun. 30, 2019 USD ($) participant | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($) | Sep. 30, 2019 USD ($) | Jun. 30, 2019 USD ($) | Dec. 31, 2020 USD ($) | Dec. 31, 2019 USD ($)
German Wholesale Business |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Pension liabilities derecognized |  | $ 187 |  |  |  |  |
Changes in retirement-related benefit plans | German Wholesale Business |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Accumulated other comprehensive loss derecognized |  | 24 |  |  |  |  |
Pension Plan |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Net periodic pension expense |  | 4 | $ 16 |  |  | $ 17 | $ 151
Cash contributions to the plans |  | $ 8 | 120 |  |  | $ 19 | 132
Percentage threshold of greater of projected benefit obligation or market value of assets (percent) |  | 10.00% |  |  |  | 10.00% |
Pension Plan | United States |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Number of participants elected to receive settlement | participant | 1,300 |  |  |  |  |  |
Lump sum payments under settlement | $ 49 |  |  |  |  |  |
Pre-tax settlement expense |  |  |  |  | $ 17 |  | 122
Annuity contracts purchased |  |  |  | $ 280 |  |  |
Pension Plan | United States | Other income (expense) |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Pre-tax settlement expense |  |  |  | $ 105 |  |  |
Pension Plan | Executive Benefit Retirement Plan |  |  |  |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |  |  |  |
Cash payment for retirement plan |  |  | $ 114 |  |  |  | $ 114

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