Marketable Securities and Held-to-Maturity Debt Securities - Current and non-current (Details) - USD ($) $ in Millions |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Marketable Securities | ||
| Current marketable securities | $ 404 | $ 98 |
| Non-current marketable securities | 30 | 43 |
| Total marketable securities | 434 | 141 |
| Corporate debt securities | ||
| Marketable Securities | ||
| Current marketable securities | 7 | |
| Commercial paper | ||
| Marketable Securities | ||
| Current marketable securities | 237 | 85 |
| Certificates of deposit/time deposits | ||
| Marketable Securities | ||
| Current marketable securities | 31 | 10 |
| U.S. treasury securities | ||
| Marketable Securities | ||
| Current marketable securities | 125 | |
| U.S. municipal securities | ||
| Marketable Securities | ||
| Current marketable securities | 4 | 3 |
| Non-current marketable securities | $ 30 | $ 43 |