Share-Based Payments - Data Related to All Performance Share Awards (PSAs) (Details) - Performance Shares [Member] shares in Millions, $ in Millions |
12 Months Ended | ||
|---|---|---|---|
|
Dec. 31, 2019
USD ($)
|
Dec. 31, 2018
USD ($)
|
Dec. 31, 2017
USD ($)
Employee
shares
|
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total fair value of shares vested | $ | $ 64 | $ 4 | $ 58 |
| Total compensation cost related to nonvested awards not yet recognized, pre-tax | $ | $ 34 | $ 41 | $ 34 |
| Weighted-average period over which nonvested award cost is expected to be recognized (years) | 1 year 9 months 18 days | 1 year 9 months 18 days | 1 year 9 months 18 days |
| Number of shares modified to accelerate vesting | shares | 1.1 | ||
| Number of employees affected by plan modification | Employee | 90 | ||
| Number of shares scheduled for near-term vesting | shares | 1.1 | ||