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