Marketable Investment Securities, Restricted Cash and Cash Equivalents, and Other Investment Securities - Other Income Expense (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Other Income (Expense)
Marketable investment securities - gains (losses) on sales/exchanges	$ 5,393	$ 2,487	$ 6,139	$ 4,759
Marketable investment securities - unrealized gains (losses) on equity 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	1,376	(440)	1,844	2,759
Total	$ 21,432	$ 3,167	$ (13,376)	$ 7,912