Marketable Securities and Equity Investments - Additional Information (Details) - USD ($) |
12 Months Ended | ||
|---|---|---|---|
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
|
| Summary of cash equivalents and marketable securities | |||
| Cash | $ 2,800,000,000 | $ 2,300,000,000 | |
| Other-than-temporary declines in fair value of available-for-sale debt securities | 0 | 0 | $ 0 |
| Net unrealized gains | 136,167,000 | 143,175,000 | 2,558,000 |
| Weighted-average cost basis | 51,427,000 | 113,829,000 | |
| Publicly Traded Companies Sale | |||
| Summary of cash equivalents and marketable securities | |||
| Proceeds received | 437,567,000 | 94,936,000 | $ 0 |
| Weighted-average cost basis | 103,332,000 | $ 29,825,000 | |
| Other assets | |||
| Summary of cash equivalents and marketable securities | |||
| Equity securities without readily determinable fair value, amount | $ 20,800,000 | ||