Long-Term Financing Receivables (Reserve and Additional Information) (Details) - USD ($) $ in Millions |
Sep. 30, 2017 |
Dec. 31, 2016 |
|---|---|---|
| Receivables [Abstract] | ||
| Long Term Receivables High Credit Risk Percentage | 11.00% | 13.00% |
| Financing Receivable Reserve For Credit Losses And Exposure | $ 17 | $ 17 |