Pension and Postretirement Benefit Plans - Pension Asset Fair Value Level 3 (Details) - Qualified and Non-qualified Pension Benefits - International - Funded - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Benefit Plan Information | ||
| Foreign currency exchange | $ 346 | $ (560) |
| Level 3 | ||
| Benefit Plan Information | ||
| Foreign currency exchange | (13) | 16 |
| Defined benefit plan increases related to net purchases and unrealized gains losses | $ 48 | |
| Defined benefit plan decreases related to net purchases and unrealized gains losses | $ (11) | |