Investments in Affiliates (Equity Method Investment, Summarized Financial Data) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020	Jun. 30, 2021	Dec. 31, 2020	Jun. 30, 2020	Dec. 31, 2019
Assets:
Current assets	$ 22,479		$ 22,479			$ 34,091
Total assets	293,448		293,448			254,469
Liabilities and Shareholder's Equity:
Current liabilities	12,293		12,293			4,841
Total liabilities	52,174		52,174			44,936
Stockholder's Equity	241,274	$ 190,183	241,274	$ 190,183	$ 258,139	209,533	$ 146,231	$ 350,027
Statement of Operations Data:
Operating (loss) income	(8,745)	4,129	(12,374)	680
Interest expense	(8)	(9)	(19)	(20)
Income tax (provision) benefit	829	(309)	1,252	(956)
Telesat Canada [Member]
Assets:
Current assets	1,304,567		1,304,567			703,210
Total assets	4,501,504		4,501,504			3,943,875
Liabilities and Shareholder's Equity:
Current liabilities	150,873		150,873			129,849
Long-term debt, including current portion	2,979,716		2,979,716			2,483,256
Total liabilities	3,597,358		3,597,358			3,140,747
Stockholder's Equity	904,146		904,146			$ 803,128
Statement of Operations Data:
Revenues	153,334	152,081	457,052	460,407
Operating expenses	(33,099)	(32,325)	(115,594)	(101,106)
Depreciation and amortization	(43,410)	(44,888)	(131,977)	(133,336)
Other operating income (expense)	(23)	(26)	(587)	(182)
Operating (loss) income	76,802	74,842	208,894	225,783
Interest expense	(40,501)	(37,715)	(111,517)	(115,947)
Foreign exchange gain (loss)	(55,138)	48,943	908	(74,387)
Gain (loss) on financial instruments	3,955	246	7,749	(11,643)
Other income (loss)	(88)	527	(1,164)	4,865
Income tax (provision) benefit	(10,590)	(9,053)	(38,273)	(18,509)
Net income (loss)	$ (25,560)	$ 77,790	$ 66,597	$ 10,162