Financial Instruments - Investments in Debt and Marketable Equity Securities Disclosure (Details) - USD ($) $ in Thousands	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	$ 735,387	$ 925,276
Restricted cash	52,295	20,544
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	787,682	945,820	$ 360,454	$ 247,448
Fair Value, Measurements, Recurring
Cost or Amortized Cost
Restricted cash	52,295	20,544
Cash, cash equivalents, and available-for-sale debt securities, amortized cost	853,325	1,089,122
Unrealized Gains (Losses)
Unrealized Gains	59	181
Unrealized Losses	(12)	0
Estimated Fair Value
Cash equivalents	632,800	892,361
Cash, cash equivalents, and available-for-sale debt securities	853,372	1,089,303
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	787,682	945,820
Short-term Investments
Short-term Investments	29,605	131,561
Long-term Investments
Long-term investments	36,085	11,922
U.S. treasury securities | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Debt securities, available-for-sale, amortized cost	53,743	137,502
Unrealized Gains (Losses)
Unrealized Gains	45	159
Unrealized Losses	(12)	0
Estimated Fair Value
Debt securities, available-for-sale	53,776	137,661
Short-term Investments
Short-term Investments	24,598	131,561
Long-term Investments
Long-term investments	29,178	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	14	22
Unrealized Losses	0	0
Estimated Fair Value
Debt securities, available-for-sale	11,914	11,922
Short-term Investments
Short-term Investments	5,007	0
Long-term Investments
Long-term investments	6,907	11,922
Cash | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	102,587	32,915
Estimated Fair Value
Cash equivalents	102,587	32,915
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	102,587	32,915
Money markets funds | Fair Value, Measurements, Recurring
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	632,800	886,261
Estimated Fair Value
Cash equivalents	632,800	886,261
Cash, Cash Equivalents, Restricted Cash
Cash, cash equivalents, restricted cash and restricted cash equivalents	632,800	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