Investments and Fair Value Measurement - Unrealized Gain (Loss) on Non-Marketable Securities (Details) - USD ($) $ in Millions |
12 Months Ended | |
|---|---|---|
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Fair Value Disclosures [Abstract] | ||
| Upward adjustments | $ 0 | $ 1,984 |
| Downward adjustments (including impairment) | 0 | 0 |
| Total unrealized gain for non-marketable equity securities | $ 0 | $ 1,984 |