Supplemental Balance Sheet and Cash Flow Information - Cash, Cash Equivalents And Restricted Cash (Details) - USD ($) $ in Millions |
Mar. 31, 2018 |
Dec. 31, 2017 |
Mar. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|---|---|
| Text Block [Abstract] | ||||
| Cash and cash equivalents | $ 479 | $ 603 | $ 423 | $ 707 |
| Restricted cash included in other current assets | 8 | 3 | 9 | 5 |
| Restricted cash included in other noncurrent assets | 4 | 4 | 4 | 4 |
| Total cash, cash equivalents and restricted cash | $ 491 | $ 610 | $ 436 | $ 716 |