Share-Based Payments - Data Related to All Portfolio Performance Shares Activity (Details) - Portfolio Performance Shares [Member] - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||
| Total fair value of shares vested | $ 136 | $ 169 | $ 131 |
| Total compensation cost related to nonvested awards not yet recognized, pre-tax | $ 87 | $ 102 | $ 94 |
| 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 8 months 12 days |