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		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment Securities
Marketable investment securities - gains (losses) on sales/exchanges	$ 5,380	$ 1,803	$ 6,121	$ 1,803
Marketable investment securities - unrealized gains (losses) on trading securities	16,441		(20,848)
Costs related to early redemption of debt	(2,537)		(2,716)
Equity in earnings	759	1,120	2,205	394
Other	1,372	(446)	1,856	1,228
Total	$ 21,415	$ 2,477	$ (13,382)	$ 3,425