Share-Based Payments - Data Related to All Portfolio Performance Shares Activity (Details) - Portfolio Performance Shares [Member] shares in Thousands, $ in Millions |
12 Months Ended | ||||
|---|---|---|---|---|---|
|
Dec. 31, 2018
USD ($)
Employee
shares
|
Dec. 31, 2017
USD ($)
|
Dec. 31, 2016
USD ($)
|
|||
| Share-based Compensation Arrangement by Share-based Payment Award [Line Items] | |||||
| Total fair value of shares vested | [1] | $ 169 | $ 131 | $ 118 | |
| Total compensation cost related to nonvested awards not yet recognized, pre-tax | $ 102 | $ 94 | $ 93 | ||
| Weighted-average period over which nonvested award cost is expected to be recognized (years) | 1 year 9 months 18 days | 1 year 8 months 12 days | 1 year 9 months 18 days | ||
| Number of shares modified to accelerate vesting | shares | 200 | ||||
| Number of employees affected by plan modification | Employee | 140 | ||||
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