Significant Accounting Policies - Reconciliation Of Cash And Cash Equivalents, And Restricted Cash Reported (Details) - USD ($) $ in Millions |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
Dec. 31, 2016 |
|---|---|---|---|---|
| Accounting Policies [Abstract] | ||||
| Cash and cash equivalents | $ 60 | $ 130 | ||
| Restricted funds | 31 | 28 | ||
| Restricted funds included in other long-term assets | 0 | 1 | ||
| Cash and cash equivalents and restricted funds as presented on the Consolidated Statements of Cash Flows | $ 91 | $ 159 | $ 83 | $ 99 |