Long-Term Financing Receivables (Reserve and Additional Information) (Details) - USD ($) $ in Millions |
Jun. 30, 2018 |
Dec. 31, 2017 |
---|---|---|
Receivables [Abstract] | ||
Long Term Receivables High Credit Risk | $ 140 | $ 170 |
Financing Receivable, Allowance for Credit Losses, Individually Evaluated for Impairment | $ 17 | $ 17 |