Investments and Fair Value Measurement - Unrealized Gain (Loss) on Non-Marketable Securities (Details) - USD ($) $ in Millions |
3 Months Ended | 6 Months Ended | ||
|---|---|---|---|---|
Jun. 30, 2021 |
Jun. 30, 2020 |
Jun. 30, 2021 |
Jun. 30, 2020 |
|
| Fair Value Disclosures [Abstract] | ||||
| Upward adjustments | $ 0 | $ 0 | $ 71 | $ 0 |
| Downward adjustments (including impairment) | 0 | 0 | 0 | (1,690) |
| Total unrealized gain (loss) for non-marketable equity securities | $ 0 | $ 0 | $ 71 | $ (1,690) |