Investments in Affiliates (Equity Method Investment, Summarized Financial Data) (Details) - Telesat Canada [Member] - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017	Dec. 31, 2017
Statement of Operations Data:
Revenues	$ 174,010	$ 170,151	$ 522,990	$ 514,800
Operating expenses	(34,268)	(34,101)	(91,804)	(112,876)
Depreciation, amortization and stock-based compensation	(47,946)	(49,741)	(144,732)	(145,875)
Gain (loss) on disposition of long lived asset	848	(204)	835	(220)
Operating income (loss)	92,644	86,105	287,289	255,829
Interest expense	(43,063)	(37,901)	(130,671)	(111,765)
Foreign exchange gains (loss)	42,784	103,099	(66,294)	193,259
Gain (loss) on financial instruments	(202)	(6,542)	30,414	(17,471)
Other income (expense)	3,204	1,531	7,795	1,305
Income tax provision	(7,605)	(16,114)	(39,190)	(35,571)
Net income (loss)	87,762	$ 130,178	89,343	$ 285,586
Current assets	576,052		576,052		$ 445,104
Total assets	4,054,930		4,054,930		4,082,472
Current liabilities	157,103		157,103		126,100
Long-term debt, including current portion	2,764,075		2,764,075		2,829,911
Total liabilities	3,474,619		3,474,619		3,538,656
Shareholders' equity/Members' equity (deficit)	$ 580,311		$ 580,311		$ 543,816