Investments in Affiliates (Equity Method Investment, Summarized Financial Data) (Details) - Telesat Canada [Member] - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017
Statement of Operations Data:
Revenues	$ 164,114	$ 167,538	$ 348,980	$ 344,649
Operating expenses	(26,933)	(36,788)	(57,536)	(78,776)
Depreciation, amortization and stock-based compensation	(48,287)	(47,637)	(96,786)	(96,134)
Gain (loss) on disposition of long lived asset	(15)	2	(13)	(16)
Operating income (loss)	88,879	83,115	194,645	169,723
Interest expense	(42,520)	(37,071)	(87,608)	(73,864)
Foreign exchange gains (loss)	(45,777)	72,309	(109,078)	90,160
Gain (loss) on financial instruments	(1,767)	(7,316)	30,616	(10,929)
Other income (expense)	2,973	(686)	4,591	(225)
Income tax provision	(7,815)	(9,619)	(31,585)	(19,457)
Net income (loss)	(6,027)	$ 100,732	1,581	$ 155,408
Current assets	498,819		498,819		$ 445,104
Total assets	3,963,123		3,963,123		4,082,472
Current liabilities	141,182		141,182		126,100
Long-term debt, including current portion	2,768,248		2,768,248		2,829,911
Total liabilities	3,468,143		3,468,143		3,538,656
Shareholders' equity/Members' equity (deficit)	$ 494,980		$ 494,980		$ 543,816