Pension and Postretirement Benefit Plans and Defined Contribution Plans - One-Percentage-Point Increase or Decrease in the Healthcare Cost Trend Rate (Details) - Postretirement Benefits Plan [Member] $ in Millions |
12 Months Ended |
|---|---|
|
Dec. 31, 2018
USD ($)
| |
| Defined Benefit Plan Disclosure [Line Items] | |
| Effect on total service and interest cost components, increase | $ 3 |
| Effect on total service and interest cost components, decrease | (2) |
| Effect on postretirement benefit obligation, increase | 35 |
| Effect on postretirement benefit obligation, decrease | $ (27) |