Investments in Affiliates (Equity Method Investment, Summarized Financial Data) (Details) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020	Mar. 31, 2021	Dec. 31, 2020	Mar. 31, 2020	Dec. 31, 2019
Assets:
Current assets	$ 26,111		$ 26,111			$ 34,091
Total assets	303,066		303,066			254,469
Liabilities and Shareholder's Equity:
Current liabilities	4,918		4,918			4,841
Total liabilities	44,927		44,927			44,936
Stockholder's Equity	258,139	$ 146,231	258,139	$ 146,231	$ 238,433	209,533	$ 259,974	$ 350,027
Statement of Operations Data:
Operating income (loss)	(1,900)	(1,801)	(3,629)	(3,449)
Interest expense	(5)	(6)	(11)	(11)
Income tax (provision) benefit	201	1,469	423	(647)
Telesat Canada [Member]
Assets:
Current assets	1,247,156		1,247,156			703,210
Total assets	4,527,918		4,527,918			3,943,875
Liabilities and Shareholder's Equity:
Current liabilities	130,767		130,767			129,849
Long-term debt, including current portion	2,978,805		2,978,805			2,483,256
Total liabilities	3,606,651		3,606,651			3,140,747
Stockholder's Equity	921,267		921,267			$ 803,128
Statement of Operations Data:
Revenues	153,664	149,761	303,718	308,326
Operating expenses	(50,955)	(33,465)	(82,495)	(68,781)
Depreciation and amortization	(45,854)	(43,031)	(88,567)	(88,448)
Other operating income (expense)	(69)	11	(564)	(156)
Operating income (loss)	56,786	73,276	132,092	150,941
Interest expense	(37,916)	(36,685)	(71,016)	(78,232)
Foreign exchange gain (loss)	28,619	98,313	56,046	(123,330)
Gain (loss) on financial instruments	2,209	(4,884)	3,794	(11,889)
Other income (loss)	(279)	799	(1,076)	4,338
Income tax (provision) benefit	(10,773)	(10,138)	(27,683)	(9,456)
Net income (loss)	$ 38,646	$ 120,681	$ 92,157	$ (67,628)