Financial Instruments - Investments in Debt and Marketable Equity Securities Disclosure (Details) - USD ($) $ in Thousands	Sep. 30, 2021	Dec. 31, 2020	Sep. 30, 2020	Dec. 31, 2019
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	$ 562,714	$ 925,276
Restricted cash	74,532	20,544
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	637,246	945,820	$ 387,966	$ 247,448
Fair Value, Measurements, Recurring
Cost or Amortized Cost
Restricted cash	74,532	20,544
Cash, cash equivalents, and available-for-sale debt securities, amortized cost	715,107	1,089,122
Unrealized Gains (Losses)
Unrealized Gains	4,213	181
Unrealized Losses	(8)	0
Estimated Fair Value
Cash equivalents	501,432	892,361
Cash, cash equivalents, and available-for-sale debt securities	719,312	1,089,303
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	637,246	945,820
Short-term Investments
Short-term Investments	28,578	131,561
Long-term Investments
Long-term investments	53,488	11,922
U.S. treasury securities | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Debt securities, available-for-sale, amortized cost	65,461	137,502
Unrealized Gains (Losses)
Unrealized Gains	16	159
Unrealized Losses	(8)	0
Estimated Fair Value
Debt securities, available-for-sale	65,469	137,661
Short-term Investments
Short-term Investments	11,981	131,561
Long-term Investments
Long-term investments	53,488	0
Agency bonds | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Debt securities, available-for-sale, amortized cost	11,900	11,900
Unrealized Gains (Losses)
Unrealized Gains	12	22
Unrealized Losses	0	0
Estimated Fair Value
Debt securities, available-for-sale	11,912	11,922
Short-term Investments
Short-term Investments	11,912	0
Long-term Investments
Long-term investments	0	11,922
Equity securities
Cost or Amortized Cost
Debt securities, available-for-sale, amortized cost	500
Unrealized Gains (Losses)
Unrealized Gains	4,185
Unrealized Losses	0
Estimated Fair Value
Debt securities, available-for-sale	4,685
Short-term Investments
Short-term Investments	4,685
Long-term Investments
Long-term investments	0
Equity securities | Fair Value, Measurements, Recurring
Short-term Investments
Short-term Investments	4,685
Cash | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	61,282	32,915
Estimated Fair Value
Cash equivalents	61,282	32,915
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	61,282	32,915
Money markets funds | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	501,432	886,261
Estimated Fair Value
Cash equivalents	501,432	886,261
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	501,432	886,261
U.S. treasury securities | Fair Value, Measurements, Recurring
Estimated Fair Value
Cash equivalents		6,100
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	$ 0	$ 6,100