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, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019
Amortization of prior service credits and net actuarial loss, Before-Tax Amount	[1]	$ 340	$ 271	$ 642	$ 501
Equity in Telesat-related other comprehensive income (loss), Before-Tax Amount		(17,454)	(6,861)	13,609	(13,450)
Other comprehensive income (loss), Before-Tax Amount		(17,114)	(6,590)	14,251	(12,949)
Amortization of prior service credits and net actuarial loss, Tax (Provision) Benefit		(71)	(58)	(134)	(106)
Equity in Telesat-related other comprehensive income (loss), Tax (Provision) Benefit		6	2	(6)	3
Other comprehensive income, Tax (Provision) Benefit		(65)	(56)	(140)	(103)
Amortization of prior service credits and net actuarial gain (loss), Net-of-Tax Amount		269	213	508	395
Equity in Telesat-related other comprehensive income (loss), Net-of-Tax Amount		(17,448)	(6,859)	13,603	(13,447)
Other comprehensive income (loss), Net-of-tax Amount		$ (17,179)	$ (6,646)	$ 14,111	$ (13,052)

[1] Reclassifications are included in other expense.