Financial Instruments - Investments in Debt and Marketable Equity Securities Disclosure (Details) - USD ($) $ in Thousands	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	$ 1,241,255	$ 925,276
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	1,343,045	945,820	$ 230,712	$ 247,448
Fair Value, Measurements, Recurring
Cost or Amortized Cost
Restricted cash	101,790	20,544
Cash, cash equivalents, and available-for-sale debt securities, amortized cost	1,490,663	1,089,122
Unrealized Gains (Losses)
Unrealized Gains	132	181
Unrealized Losses	(1)	0
Estimated Fair Value
Cash equivalents	617,502	892,361
Cash, cash equivalents, and available-for-sale debt securities	1,490,794	1,089,303
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	1,343,045	945,820
Short-term Investments
Short-term Investments	140,843	131,561
Long-term Investments
Long-term investments	6,906	11,922
U.S. treasury securities | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Debt securities, available-for-sale, amortized cost	145,630	137,502
Unrealized Gains (Losses)
Unrealized Gains	125	159
Unrealized Losses	0	0
Estimated Fair Value
Debt securities, available-for-sale	145,755	137,661
Short-term Investments
Short-term Investments	140,843	131,561
Long-term Investments
Long-term investments	0	0
Agency bonds | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Debt securities, available-for-sale, amortized cost	6,900	11,900
Unrealized Gains (Losses)
Unrealized Gains	7	22
Unrealized Losses	(1)	0
Estimated Fair Value
Debt securities, available-for-sale	6,906	11,922
Short-term Investments
Short-term Investments	0	0
Long-term Investments
Long-term investments	6,906	11,922
Cash | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	623,753	32,915
Estimated Fair Value
Cash equivalents	623,753	32,915
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	623,753	32,915
Money markets funds | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	612,590	886,261
Estimated Fair Value
Cash equivalents	612,590	886,261
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	612,590	886,261
U.S. treasury securities | Fair Value, Measurements, Recurring
Estimated Fair Value
Cash equivalents	4,912	6,100
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	$ 4,912	$ 6,100