Variable Interest Entities (VIEs) (Narrative) (Details) - USD ($) $ in Millions |
3 Months Ended | |
|---|---|---|
Mar. 31, 2018 |
Mar. 31, 2017 |
|
| Variable Interest Entity | ||
| Unfunded commitments to fund tax credit entities | $ 165 | |
| Amount of financial or other support not contractually required provided by the Corporation to VIEs | 0 | $ 0 |
| Low Income Housing Tax Credit Entities | ||
| Variable Interest Entity | ||
| Exposure to loss as a result of involvement with VIEs | 426 | |
| Other Tax Credit Entities | ||
| Variable Interest Entity | ||
| Exposure to loss as a result of involvement with VIEs | $ 7 | |