Related Party Transactions (Narrative) (Details) - USD ($)	3 Months Ended				6 Months Ended		12 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2013	Jun. 30, 2018	Jun. 30, 2017	Dec. 31, 2017	Dec. 31, 2009
Related Party Transaction [Line Items]
Distribution received from affiliate						$ 242,735,000
Transaction, Consulting Agreement [Member] | Director [Member]
Related Party Transaction [Line Items]
Related party transaction, date					Dec. 14, 2012
Transaction fee	$ 360,000	$ 360,000			$ 720,000	720,000
Transaction income during the period	$ 11,250	15,750			22,500	31,500
Monthly Fee [Member] | Transaction, Consulting Agreement [Member] | Director [Member]
Related Party Transaction [Line Items]
Transaction fee					$ 120,000
Telesat Canada [Member]
Related Party Transaction [Line Items]
Economic interest in affiliates	62.70%				62.70%		62.70%
Common stock, percentage acquired by an unaffiliated third party					90.00%
Duration for shares to be paid, days					10 days
Distribution received from affiliate			$ 242,700,000
Telesat Canada [Member] | Transaction, Consulting Agreement [Member]
Related Party Transaction [Line Items]
Related party transaction, date					Oct. 31, 2007
Transaction income during the period	$ 1,250,000	$ 1,250,000			$ 2,500,000	2,500,000
Transaction payments received during the period					2,400,000	$ 2,400,000
Telesat Canada [Member] | Annual Fee [Member] | Transaction, Consulting Agreement [Member]
Related Party Transaction [Line Items]
Transaction fee					5,000,000
Telesat Canada [Member] | Annual Fee [Member] | Transaction, Welfare Plan Participation Administrative Fee [Member]
Related Party Transaction [Line Items]
Transaction fee					$ 100,000
Telesat Canada [Member] | Years 2003 to 2006 [Member] | Brazil [Member]
Related Party Transaction [Line Items]
Tax assessment imposed audit								$ 1,000,000
XTAR, LLC [Member]
Related Party Transaction [Line Items]
Percentage of ownership interest	56.00%				56.00%
XTAR, LLC [Member] | Transaction, Management Agreement [Member]
Related Party Transaction [Line Items]
Allowance for doubtful accounts receivable, noncurrent	$ 6,600,000				$ 6,600,000		$ 6,600,000
Due from Affiliates	$ 6,700,000				$ 6,700,000		$ 6,800,000
Management fee charged as a percentage of revenue				3.70%
MHR Funds [Member]
Related Party Transaction [Line Items]
Percentage of outstanding voting common stock					39.90%		39.90%
Percentage of combined ownership of voting and non-voting common stock	58.40%				58.40%		58.40%