Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income and Related Tax Effects) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2020	Mar. 31, 2019
Amortization of prior service credits and net actuarial loss, Before-Tax Amount	[1]	$ 302	$ 230
Proportionate share of Telesat Holdco other comprehensive income (loss), Before-Tax Amount		31,063	(6,589)
Other comprehensive income (loss), Before-Tax Amount		31,365	(6,359)
Amortization of prior service credits and net actuarial loss, Tax (Provision) Benefit		(63)	(48)
Proportionate share of Telesat Holdco other comprehensive income (loss), Tax (Provision) Benefit		(12)	1
Other comprehensive income, Tax (Provision) Benefit		(75)	(47)
Amortization of prior service credits and net actuarial gain (loss), Net-of-Tax Amount		239	182
Proportionate share of Telesat Holdco other comprehensive income (loss), Net-of-Tax Amount		31,051	(6,588)
Other comprehensive income (loss), Net-of-tax Amount		$ 31,290	$ (6,406)

[1] Reclassifications are included in other expense.