Investment Securities (Gross Realized Gain Losses) (Details) - USD ($) $ in Millions |
3 Months Ended | 9 Months Ended | ||
|---|---|---|---|---|
Sep. 30, 2015 |
Sep. 30, 2014 |
Sep. 30, 2015 |
Sep. 30, 2014 |
|
| Schedule of Available-for-sale Securities [Line Items] | ||||
| Gains | $ 21 | $ 1 | $ 122 | $ 37 |
| Losses, including impairments | (6) | (5) | (41) | (18) |
| Total | 15 | (4) | 81 | 19 |
| Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds | $ 6,022 | $ 623 | 9,322 | $ 1,995 |
| Trinity [Member] | ||||
| Schedule of Available-for-sale Securities [Line Items] | ||||
| Available-for-sale Securities, Gross Realized Gains (Losses), Sale Proceeds | $ 6,486 | |||