Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment Securities - Unrealized Gain (Losses) On Marketable Investment Securities (Details) - USD ($) $ in Thousands	Jun. 30, 2020	Dec. 31, 2019
Components of our available-for-sale investments
Marketable Investment Securities	$ 40,202	$ 417,094
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains		96
Unrealized Losses		(1)
Unrealized Gains Losses, Net		95
Accumulated net unrealized losses
Accumulated net unrealized gain (loss), before tax, in accumulated other comprehensive income (loss)	0	(1,000)
Accumulated net unrealized gain (loss), net of tax, in accumulated other comprehensive income (loss)	0	(1,000)
Contractual maturities of restricted and non-restricted marketable investment securities
Debt securities with contractual maturities within one year	189	196
US Treasury and agency securities
Components of our available-for-sale investments
Marketable Investment Securities		10,016
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains		32
Unrealized Gains Losses, Net		32
Commercial paper
Components of our available-for-sale investments
Marketable Investment Securities	40,000	369,397
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains		2
Unrealized Gains Losses, Net		2
Corporate securities
Components of our available-for-sale investments
Marketable Investment Securities		28,796
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains		4
Unrealized Losses		(1)
Unrealized Gains Losses, Net		3
Other
Components of our available-for-sale investments
Marketable Investment Securities	$ 202	8,885
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains		58
Unrealized Gains Losses, Net		$ 58