Income Taxes - Changes in Gross Liability Excluding Interest and Penalties for Unrecognized Tax Benefits (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Reconciliation of Unrecognized Tax Benefits, Excluding Amounts Pertaining to Examined Tax Returns [Roll Forward] | ||
| Beginning Balance | $ 97 | $ 106 |
| Increases in current period tax positions | 17 | 13 |
| Decreases in prior period measurement of tax positions | (4) | (22) |
| Ending Balance | $ 110 | $ 97 |