Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income and Related Tax Effects) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2019	Mar. 31, 2018
Accumulated Other Comprehensive Loss [Abstract]
Amortization of prior service credits and net actuarial loss, Before-Tax Amount	[1]	$ 230	$ 269
Proportionate share of Telesat Holdco other comprehensive income (loss), Before-Tax Amount		(6,589)	8,777
Other comprehensive income (loss), Before-Tax Amount		(6,359)	9,046
Amortization of prior service credits and net actuarial loss, Tax (Provision) Benefit		(48)	(56)
Proportionate share of Telesat Holdco other comprehensive income (loss), Tax (Provision) Benefit		1	(1,846)
Other comprehensive income, Tax (Provision) Benefit		(47)	(1,902)
Amortization of prior service credits and net actuarial gain (loss), Net-of-Tax Amount		182	213
Proportionate share of Telesat Holdco other comprehensive income (loss), Net-of-Tax Amount		(6,588)	6,931
Other comprehensive income (loss), Net-of-tax Amount		$ (6,406)	$ 7,144

[1] Reclassifications are included in other expense.