Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income and Related Tax Effects) (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2019	Jun. 30, 2018	Jun. 30, 2019	Jun. 30, 2018
Accumulated Other Comprehensive Loss [Abstract]
Amortization of prior service credits and net actuarial loss, Before-Tax Amount	[1]	$ 271	$ 263	$ 501	$ 532
Proportionate share of Telesat Holdco other comprehensive income (loss), Before-Tax Amount		(6,861)	532	(13,450)	9,309
Other comprehensive income (loss), Before-Tax Amount		(6,590)	795	(12,949)	9,841
Amortization of prior service credits and net actuarial loss, Tax (Provision) Benefit		(58)	(56)	(106)	(112)
Proportionate share of Telesat Holdco other comprehensive income (loss), Tax (Provision) Benefit		2	(111)	3	(1,957)
Other comprehensive income, Tax (Provision) Benefit		(56)	(167)	(103)	(2,069)
Amortization of prior service credits and net actuarial gain (loss), Net-of-Tax Amount		213	207	395	420
Proportionate share of Telesat Holdco other comprehensive income (loss), Net-of-Tax Amount		(6,859)	421	(13,447)	7,352
Other comprehensive income (loss), Net-of-tax Amount		$ (6,646)	$ 628	$ (13,052)	$ 7,772

[1] Reclassifications are included in other expense.