Investments and Fair Value Measurement - Fair Value of Unobservable Inputs, Assets (Details) - USD ($) $ in Millions |
3 Months Ended | 12 Months Ended | |
|---|---|---|---|
Mar. 31, 2020 |
Mar. 31, 2019 |
Dec. 31, 2019 |
|
| Total net gains (losses) | |||
| Change in unrealized loss on investments in available-for-sale securities | $ (60) | $ (4) | |
| Non-marketable Debt Securities | |||
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | |||
| Beginning balance | 2,370 | 2,370 | $ 2,370 |
| Total net gains (losses) | |||
| Included in earnings | (27) | (8) | |
| Included in other comprehensive income (loss) | 4 | ||
| Purchases | 3 | 4 | |
| Impairments | (173) | ||
| Ending balance | 2,116 | 2,370 | |
| Non-marketable equity securities | |||
| Fair Value, Assets Measured on Recurring Basis, Unobservable Input Reconciliation, Calculation [Roll Forward] | |||
| Beginning balance | 98 | $ 0 | 0 |
| Total net gains (losses) | |||
| Included in earnings | (87) | 11 | |
| Included in other comprehensive income (loss) | 0 | 0 | |
| Purchases | 10 | 56 | |
| Transfers | 31 | ||
| Impairments | 0 | ||
| Ending balance | $ 21 | $ 98 | |