Accounts Receivable (Details) - USD ($) $ in Millions |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Accounts Receivable Details [Abstract] | |||
| Allowance for doubtful accounts | $ 3 | $ 3 | |
| Allowance for doubtful accounts - receivables not expected to be collected in one year | 27 | 17 | |
| Receivables Securitization Facility [Abstract] | |||
| Total capacity to transfer undivided interests to investors under the receivables securitization facility | $ 650 | ||
| Receivables securitization facility maturity date | 2019-07 | ||
| Receivables securitization facility duration | 3 years | ||
| Value of the outstanding undivided interest held by investors under the receivables securitization facility | $ 400 | 500 | |
| Accounts receivable supporting the undivided interest held by investors | 1,400 | 1,100 | |
| Cost of the receivables securitization facility - interest expense | $ 15 | $ 6 | $ 7 |