Geographical Information (Details) - USD ($) $ in Millions |
Mar. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Revenues from External Customers and Long-Lived Assets [Line Items] | ||
| Long-lived assets | $ 1,523 | $ 1,528 |
| U.S. | ||
| Revenues from External Customers and Long-Lived Assets [Line Items] | ||
| Long-lived assets | 1,422 | 1,432 |
| Other countries | ||
| Revenues from External Customers and Long-Lived Assets [Line Items] | ||
| Long-lived assets | $ 101 | $ 96 |