Property, Equipment and Right-of-Use Assets - Operating Right-of-Use Assets and Operating Lease Liabilities (Details) - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Property, Plant and Equipment [Abstract] | ||
| Property, equipment and right-of-use assets, net | $ 748 | $ 711 |
| Other current liabilities | 125 | 106 |
| Other liabilities | $ 726 | $ 656 |
| Operating Lease, Right-of-Use Asset, Statement of Financial Position [Extensible List] | us-gaap:AssetsAbstract | us-gaap:AssetsAbstract |
| Operating Lease, Liability, Current, Statement of Financial Position [Extensible List] | us-gaap:OtherLiabilitiesCurrent | us-gaap:OtherLiabilitiesCurrent |
| Operating Lease, Liability, Noncurrent, Statement of Financial Position [Extensible List] | us-gaap:OtherLiabilitiesNoncurrent | us-gaap:OtherLiabilitiesNoncurrent |