Variable Interest Entities and Securitization Activities (Narrative) (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended |
|---|---|---|
Mar. 31, 2016 |
Dec. 31, 2015 |
|
| Variable Interest Entity | ||
| Additional maximum exposure to losses | $ 74 | $ 72 |
| Securities issued by SPEs | $ 12,600 | $ 12,900 |