Investments in Affiliates (Equity Method Investment, Summarized Financial Data) (Details) - Telesat Canada [Member] - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017
Summary Financial Data:
Revenues	$ 699,596	$ 712,390
Operating expenses	(137,400)	(152,157)
Depreciation, amortization and stock-based compensation	(205,451)	(194,203)
Insurance proceeds		4,739
Other operating income (expense)	576	(207)
Operating income	357,321	370,562
Interest expense	(176,873)	(151,528)
Foreign exchange (loss) gain	(203,005)	173,433
Gain (loss) on financial instruments	15,795	(3,516)
Other income (expense)	11,335	3,592
Income tax provision	(45,423)	(54,424)
Net (loss) income	(40,850)	338,119
Current assets	628,125	445,104
Total assets	3,942,847	4,082,472
Current liabilities	139,401	126,100
Long-term debt, including current portion	2,764,599	2,829,911
Total liabilities	3,474,504	3,538,656
Shareholders' equity	$ 468,343	$ 543,816