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Employee Benefit Plans - Benefit Cost Narrative (Details) - USD ($) $ in Millions | 3 Months Ended | 12 Months Ended
--- | --- | ---
Sep. 30, 2019 | Dec. 31, 2019 | Dec. 31, 2018 | Dec. 31, 2017
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Percent Amortized Of Unamortized Balance For Net Actuarial Gain And Losses |  | 10.00% |  |
Other Comprehensive Income (Loss), Defined Benefit Plans |  | $ (51) | $ (39) | $ (147)
Other Postretirement Benefit Plans, Defined Benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension settlement losses |  | $ 0 | $ 0 | 0
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate |  | 3.10% | 4.05% |
U.S. | Pension Plans Defined Benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension settlement losses |  | $ (62) | $ (196) | (131)
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate |  | 3.25% | 4.25% |
U.S. | Other Postretirement Benefit Plans, Defined Benefit [Member] | Pre Sixty Five Retiree[Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year |  | 7.00% |  |
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate |  | 5.00% |  |
U.S. | Other Postretirement Benefit Plans, Defined Benefit [Member] | Post Sixty Five Retiree [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Health Care Cost Trend Rate Assumed for Next Fiscal Year |  | 4.00% |  |
Defined Benefit Plan, Ultimate Health Care Cost Trend Rate |  | 5.00% |  |
U.S. | Qualified Plan [Member] | Prudential Benefit Obligation [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Change In Defined Benefit Assets |  |  | $ 730 |
U.S. | Qualified Plan [Member] | Pension Plans Defined Benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension settlement losses |  | $ (62) | (196) | (131)
U.S. | Qualified Plan [Member] | Pension Plans Defined Benefit [Member] | Prudential Benefit Obligation [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Change In Defined Benefit Obligation |  |  | 730 |
Change In Defined Benefit Assets |  |  | 730 |
U.S. | Qualified Plan [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member] | Prudential Benefit Obligation [Member] | Pre Sixty Five Retiree[Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate |  | 2028 |  |
U.S. | Qualified Plan [Member] | Other Postretirement Benefit Plans, Defined Benefit [Member] | Prudential Benefit Obligation [Member] | Post Sixty Five Retiree [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Defined Benefit Plan, Year that Rate Reaches Ultimate Trend Rate |  | 2028 |  |
Foreign Plan [Member] | Pension Plans Defined Benefit [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Pension settlement losses |  | $ 0 | $ 0 | $ 0
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate |  | 2.35% | 3.05% |
Foreign Plan [Member] | Qualified Plan [Member] | Pension Plans Defined Benefit [Member] | Certain United Kingdom Assets [Member] |  |  |  |
Defined Benefit Plan Disclosure [Line Items] |  |  |  |
Change In Defined Benefit Assets | $ 43 |  |  |
Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Discount Rate | 1.80% |  | 2.90% |

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