Financial Instruments (Counterparty credit risk) (Details) $ in Millions |
Sep. 30, 2015
USD ($)
|
|---|---|
| Counterparty credit risk | |
| Total Collateral Received | $ 4,354 |
| Fair value of collateral posted to counterparties for derivative obligations | 895 |
| Exposure To Counterparties Including Interest Net Collateral Excluding Derivatives | 674 |
| Cash [Member] | |
| Counterparty credit risk | |
| Total Collateral Received | 2,844 |
| Securities Held By Third Parties [Member] | |
| Counterparty credit risk | |
| Securities Held as Collateral, at Fair Value | $ 1,510 |