Financial Instruments - Investments in Debt and Marketable Equity Securities Disclosure (Details) - USD ($) $ in Thousands	Mar. 31, 2020	Dec. 31, 2019
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	$ 213,940	$ 234,679
Restricted cash	16,772	12,769
Cash, cash equivalents, and available-for-sale debt securities, amortized cost	331,325	348,446
Unrealized Gains (Losses)
Unrealized Gains	574	31
Unrealized Losses	(6)	(22)
Estimated Fair Value
Cash, cash equivalents, and available-for-sale debt securities	331,893	348,455
Short-term Investments
Short-term investments	75,049	70,029
Long-term Investments
Long-term investments	26,711	30,978
Fair Value, Inputs, Level 1 | U.S. treasury securities
Cost or Amortized Cost
Debt securities, available-for-sale, amortized cost	99,192	100,998
Unrealized Gains (Losses)
Unrealized Gains	574	31
Unrealized Losses	0	(22)
Estimated Fair Value
Debt securities, available-for-sale	99,766	101,007
Short-term Investments
Short-term investments	75,049	70,029
Long-term Investments
Long-term investments	24,717	30,978
Fair Value, Inputs, Level 1 | Agency bonds
Cost or Amortized Cost
Debt securities, available-for-sale, amortized cost	2,000
Unrealized Gains (Losses)
Unrealized Gains	0
Unrealized Losses	(6)
Estimated Fair Value
Debt securities, available-for-sale	1,994
Short-term Investments
Short-term investments	0
Long-term Investments
Long-term investments	1,994
Cash
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	18,831	13,237
Money Market Funds | Fair Value, Inputs, Level 1
Cost or Amortized Cost
Cash and cash equivalents, at carrying value	$ 194,530	$ 221,442