Financial Instruments - Cost, Amortized Cost, Gross Unrealized Gains & Losses, and Estimated Fair Market Value (Details) - USD ($) $ in Thousands	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	$ 591,003	$ 925,276	$ 234,679
Restricted cash	127,278	20,544	12,769
Estimated Fair Value
Restricted cash	127,278	20,544	12,769
Cash, Cash Equivalents, Restricted Cash
Cash, Cash Equivalents, Restricted Cash	718,281	945,820	$ 247,448	$ 439,055
Fair Value, Measurements, Recurring
Cost or Amortized Cost
Restricted cash	127,278	20,544
Cash, cash equivalents, and available-for-sale debt securities, amortized cost	802,430	1,089,122
Unrealized Gains (Losses)
Unrealized Gains	4,620	181
Unrealized Losses	(204)	0
Estimated Fair Value
Cash and cash equivalents, fair value disclosure	509,971	892,361
Restricted cash	127,278	20,544
Cash, cash equivalents, and available-for-sale debt securities	806,846	1,089,303
Cash, Cash Equivalents, Restricted Cash
Cash, Cash Equivalents, Restricted Cash	718,281	945,820
Short-term Investments
Short-term Investments	33,737	131,561
Long-term Investments
Long-term Investments	54,828	11,922
U.S. treasury securities | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Debt securities, available-for-sale, amortized cost	71,749	137,502
Unrealized Gains (Losses)
Unrealized Gains	1	159
Unrealized Losses	(204)	0
Estimated Fair Value
Debt securities, available-for-sale	71,546	137,661
Short-term Investments
Short-term Investments	16,718	131,561
Long-term Investments
Long-term Investments	54,828	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	6	22
Unrealized Losses	0	0
Estimated Fair Value
Debt securities, available-for-sale	11,906	11,922
Short-term Investments
Short-term Investments	11,906	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	4,613
Unrealized Losses	0
Estimated Fair Value
Debt securities, available-for-sale	5,113
Short-term Investments
Short-term Investments	5,113
Equity securities | Fair Value, Measurements, Recurring
Short-term Investments
Short-term Investments	5,113
Long-term Investments
Long-term Investments	0
Cash | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	81,032	32,915
Estimated Fair Value
Cash and cash equivalents, fair value disclosure	81,032	32,915
Cash, Cash Equivalents, Restricted Cash
Cash, Cash Equivalents, Restricted Cash	81,032	32,915
Money markets funds | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	509,971	886,261
Estimated Fair Value
Cash and cash equivalents, fair value disclosure	509,971	886,261
Cash, Cash Equivalents, Restricted Cash
Cash, Cash Equivalents, Restricted Cash	509,971	886,261
U.S. treasury securities | Fair Value, Measurements, Recurring
Estimated Fair Value
Cash and cash equivalents, fair value disclosure		6,100
Cash, Cash Equivalents, Restricted Cash
Cash, Cash Equivalents, Restricted Cash	$ 0	$ 6,100