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Pension and Other Postretirement Benefits - Schedule of Weighted Average Assumptions Used to Determine Benefit Obligations (Details) $ in Millions | 12 Months Ended
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Dec. 31, 2019 | Dec. 31, 2018 USD ($) | Dec. 31, 2017 USD ($) | Dec. 31, 2016 USD ($)
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |  |  |
Discount rate |  | 4.35% | 3.75% |
Rate of compensation increase |  | 3.50% | 3.50% |
Cash balance plan interest crediting rate |  | 3.00% | 3.00% |
Average duration for plans' projected cash flows |  | 10 years |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] |  |  |  |
Discount rate to calculate service cost |  | 3.75% | 4.20% | 4.29%
Discount rate to calculate interest cost |  | 3.30% | 3.60% | 3.15%
Expected long-term rate of return on plan assets |  | 7.00% | 7.75% | 7.75%
Rate of compensation increase |  | 3.50% | 3.50% | 3.50%
Cash balance plan interest crediting rate |  | 0.0300 | 0.0300 | 0.0300
Period expected long-term rate of return is applied |  | 5 years |  |
Number of years over actual annual healthcare cost trend experience |  | 20 years |  |
Basis point of decrease identified In long term rate of return |  | 0.75% |  |
Pension benefits paid |  |  |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Benefit Obligation [Abstract] |  |  |  |
Period of observation to determine average compensation increase |  | 5 years |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] |  |  |  |
Interest cost component related to net periodic benefit cost |  | $ 24 | $ 34 | $ 84
Other postretirement benefits |  |  |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] |  |  |  |
Interest cost component related to net periodic benefit cost |  | $ 4 | $ 6 | $ 14
Number of years over actual annual healthcare cost trend experience |  | 3 years |  |
Scenario, Forecast |  |  |  |
Defined Benefit Plan, Weighted Average Assumptions Used in Calculating Net Periodic Benefit Cost [Abstract] |  |  |  |
Expected long-term rate of return on plan assets | 7.00% |  |  |

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