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	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment Securities
Marketable investment securities - gains (losses) on sales/exchanges	$ 1,803	$ 32,509	$ 14,449
Marketable investment securities - unrealized gains (losses) on trading securities	85,217
Costs related to early redemption of debt	(1,470)
Equity in earnings	2,163	2,508	4,372
Other	798	(2,212)	(1,005)
Total	$ 88,511	$ 32,805	$ 17,816