Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment Securities - Gains And Losses On Sales And Changes In Carrying Amounts Of Investments (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2017	Sep. 30, 2016	Sep. 30, 2017	Sep. 30, 2016
Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment Securities
Marketable investment securities - gains (losses) on sales/exchanges			$ 1,803	$ 32,322
Marketable investment securities - unrealized gains (losses) on trading securities	$ 39,706		39,706
Other	553	$ 1,331	2,175	684
Total	$ 40,259	$ 1,331	$ 43,684	$ 33,006