Investments in Affiliates (Narrative) (Details) $ / shares in Units, CAD in Millions	3 Months Ended						6 Months Ended	9 Months Ended		12 Months Ended
	Sep. 30, 2016 USD ($)	Mar. 31, 2016 CAD shares	Mar. 31, 2016 USD ($) shares	Dec. 31, 2015 USD ($)	Sep. 30, 2015 USD ($)	Mar. 31, 2009 USD ($)	Jun. 30, 2016 USD ($)	Sep. 30, 2016 USD ($) item $ / shares	Sep. 30, 2015 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)	Dec. 31, 2015 USD ($)	Dec. 31, 2009 USD ($)	Dec. 31, 2008 USD ($)
Investments in and Advances to Affiliates [Line Items]
Investments in affiliates	$ 114,321,000							$ 114,321,000
Equity in net income (loss) of affiliates	6,948,000				$ (38,475,000)			96,799,000	$ (90,233,000)
Net income (loss)	$ (3,892,000)				(3,555,000)			$ 59,346,000	(68,397,000)
Telesat Holdings Inc [Member]
Investments in and Advances to Affiliates [Line Items]
Economic interest in affiliates	62.70%			62.80%				62.70%				62.80%
Voting interest in affiliate	32.70%							32.70%
Share appreciation rights exercised by Telesat employees | shares		178,642	178,642
Non-voting participating preferred stock issued to Telesat Employees | shares		129,400	129,400
Equity method investee, stock options buy back, shares | shares		1,253,477	1,253,477
Equity method investee, stock options buy back, amount | CAD		CAD 24.7
Equity method investment unrecognized loss in equity				$ 57,900,000								$ 57,900,000
Equity method investment unrecognized gain in other comprehensive income												20,800,000
Investments in affiliates	$ 114,321,000			0				$ 114,321,000				0
Equity method losses previously suspended recovered			$ 57,900,000
Equity method OCI previously suspended recovered			$ 20,800,000
Equity in net income (loss) of affiliates	6,948,000				(27,913,000)			96,799,000	(74,329,000)
Total assets	4,248,874,000			3,991,301,000				4,248,874,000				3,991,301,000
Long-term debt, including current portion	2,917,704,000			2,950,726,000				2,917,704,000				2,950,726,000
Capital expenditures								153,200,000	57,000,000
Telesat Holdings Inc [Member] | Management [Member]
Investments in and Advances to Affiliates [Line Items]
Equity method investee, stock options buy back, amount | CAD		CAD 18.7
XTAR, LLC [Member]
Investments in and Advances to Affiliates [Line Items]
Investments in affiliates	0							0
Equity in net income (loss) of affiliates					(10,562,000)				$ (15,904,000)
Total assets	$ 37,668,000			44,793,000				$ 37,668,000				$ 44,793,000
Percentage of ownership interest	56.00%							56.00%
Equity method investment, impairment				13,200,000	$ 8,000,000
Equity method investee, percentage of decline in revenue over previous year												11.00%
6% Senior Notes Due May 2017 [Member] | Telesat Holdings Inc [Member]
Investments in and Advances to Affiliates [Line Items]
Interest on notes	6.00%							6.00%
Interest expense multiplier to determine EBITDA available for dividend distribution | item								1.40
Adjustments for New Accounting Pronouncement [Member] | Telesat Holdings Inc [Member]
Investments in and Advances to Affiliates [Line Items]
Total assets				(18,100,000)								$ (18,100,000)
Long-term debt, including current portion				(18,100,000)								(18,100,000)
Spainsat Lease Agreement [Member] | XTAR, LLC [Member]
Investments in and Advances to Affiliates [Line Items]
Maximum lease obligation, Annual											$ 28,000,000
Lease obligation, Annual											26,000,000
Amended lease obligation, Annual										$ 18,200,000	$ 18,200,000
Lease Obligation, Reduction							$ 4,000,000	$ 6,000,000
Lease agreement, past due														$ 32,300,000
Lease agreement, deferred amount													$ 6,700,000
Repayment term past due and deferred lease obligation, years						12 years
Deferred lease obligation, annual payment						$ 5,000,000
Discount rate for prepayment of restructured past due and deferred lease obligation						9.00%
Cumulative payments of restructured past due and deferred lease obligation								29,200,000
Equity method investment, investee past due liability	$ 24,600,000			$ 17,700,000				24,600,000				$ 17,700,000
Overstatement [Member] | Telesat Holdings Inc [Member] | Restatement Adjustment [Member]
Investments in and Advances to Affiliates [Line Items]
Equity in net income (loss) of affiliates								3,000,000
Net income (loss)								$ 1,800,000
Earnings per share, basic and diluted | $ / shares								$ 0.06