Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment Securities - Unrealized Gain (Losses) On Marketable Investment Securities (Details) - USD ($) $ in Thousands	Dec. 31, 2016	Dec. 31, 2015
Components of our available-for-sale investments
Debt securities	$ 35,616	$ 557,911
Total marketable investment securities	117,295	640,191
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains	1,404	98,196
Unrealized Losses	(143)	(673)
Unrealized Gains Losses, Net	1,261	97,523
Contractual maturities of restricted and non-restricted marketable investment securities
Debt securities with contractual maturities within one year	76,000
Debt securities with contractual maturities extending longer than one year through and including five years	41,000
Accumulated net unrealized gains (losses)
Accumulated net unrealized gains, before tax, in accumulated other comprehensive income (loss)	1,000	98,000
Accumulated net unrealized gains, net of tax, in accumulated other comprehensive income (loss)	1,000	62,000
US Treasury and agency securities
Components of our available-for-sale investments
Total marketable investment securities	81,982	82,124
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains	13	2
Unrealized Losses	(132)	(135)
Unrealized Gains Losses, Net	(119)	(133)
Corporate securities
Components of our available-for-sale investments
Total marketable investment securities	33,555	349,897
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains	1,327	29,370
Unrealized Losses		(480)
Unrealized Gains Losses, Net	1,327	28,890
Other (including restricted)
Components of our available-for-sale investments
Total marketable investment securities	1,758	47,847
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains	64	73
Unrealized Losses	(11)	(17)
Unrealized Gains Losses, Net	$ 53	56
Equity securities
Components of our available-for-sale investments
Total marketable investment securities		160,323
Unrealized Gains (Losses) on Marketable Investment Securities
Unrealized Gains		68,751
Unrealized Losses		(41)
Unrealized Gains Losses, Net		$ 68,710