Fair Value Disclosures (Borrowings Measured at Fair Value on a Recurring Basis) (Details) - USD ($) $ in Millions |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Fair Value Measurements | ||
| Borrowings at fair value | $ 51,184 | $ 46,912 |
| Recurring | ||
| Fair Value Measurements | ||
| Borrowings at fair value | 51,184 | 46,912 |
| Recurring | Equity | ||
| Fair Value Measurements | ||
| Borrowings at fair value | 24,494 | 25,903 |
| Recurring | Interest Rates | ||
| Fair Value Measurements | ||
| Borrowings at fair value | 22,343 | 19,230 |
| Recurring | Commodities | ||
| Fair Value Measurements | ||
| Borrowings at fair value | 2,735 | 298 |
| Recurring | Credit | ||
| Fair Value Measurements | ||
| Borrowings at fair value | 856 | 815 |
| Recurring | Foreign Exchange | ||
| Fair Value Measurements | ||
| Borrowings at fair value | $ 756 | $ 666 |