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Related party transaction, percentage of outstanding voting common stock.

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Tax assessment imposed by authorities on audit open for resolution

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A valuation allowance for receivables due to an Entity for more than one year from the balance sheet date that are expected to be uncollectible.

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For an unclassified balance sheet, amount of receivables due from an entity that is affiliated with the reporting entity by means of direct or indirect ownership.

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The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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Amount of distribution received from equity method investee for return of investment, classified as investing activities. Excludes distribution for return on investment, classified as operating activities.

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Amount of transactions with related party during the financial reporting period.

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Date of maturity or expiration of arrangements with a related party (for example, but not limited to, leasing and debt arrangements between related parties), in CCYY-MM-DD format.

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Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

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Related Party Transactions (Narrative) (Details) - USD ($)	3 Months Ended			12 Months Ended
	Mar. 31, 2018	Mar. 31, 2017	Dec. 31, 2013	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
Transaction income during the period	11,250	15,750
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%
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
Transaction payments received during the period	1,200,000	$ 1,200,000
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%
XTAR, LLC [Member] \| Transaction, Management Agreement [Member]
Related Party Transaction [Line Items]
Allowance for doubtful accounts receivable, noncurrent	$ 6,600,000			$ 6,600,000
Due from Affiliates	$ 7,500,000			$ 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%