Derivative Financial Instruments (Narrative) (Details) - USD ($) $ in Millions |
Sep. 30, 2016 |
Dec. 31, 2015 |
|---|---|---|
| Derivative [Line Items] | ||
| Unrealized losses on derivatives recorded in AOCI | $ (20) | $ 2 |
| Estimated amount to be reclassified from OCI into earnings during next 12 months | (7) | |
| Right to reclaim cash | 84 | 41 |
| Obligation to Return Cash | 24 | 14 |
| Cash Flow Hedges | ||
| Derivative [Line Items] | ||
| Unrealized losses on derivatives recorded in AOCI | $ (37) | $ (3) |