Investments in Affiliates (Equity Method Investment, Summarized Financial Data) (Details) - Telesat Canada [Member] - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2017
Statement of Operations Data:
Revenues	$ 184,866	$ 177,111
Operating expenses	(30,603)	(41,988)
Depreciation, amortization and stock-based compensation	(48,499)	(48,497)
Gain (loss) on disposition of long lived asset	2	(18)
Operating income (loss)	105,766	86,608
Interest expense	(45,088)	(36,793)
Foreign exchange gains (loss)	(63,301)	17,851
Gain (loss) on financial instruments	32,383	(3,613)
Other income (expense)	1,618	461
Income tax provision	(23,770)	(9,838)
Net income (loss)	7,608	$ 54,676
Current assets	477,039		$ 445,104
Total assets	4,028,918		4,082,472
Current liabilities	155,390		126,100
Long-term debt, including current portion	2,778,023		2,829,911
Total liabilities	3,520,557		3,538,656
Shareholders' equity/Members' equity (deficit)	$ 508,361		$ 543,816