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, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Accumulated Other Comprehensive Loss [Abstract]
Amortization of prior service credits and net actuarial loss, Before-Tax Amount	[1]	$ 341	$ 340	$ 740	$ 642
Equity in Telesat-related other comprehensive income (loss), Before-Tax Amount		(2,053)	(17,454)	(4,186)	13,609
Other comprehensive income (loss), Before-Tax Amount		(1,712)	(17,114)	(3,446)	14,251
Amortization of prior service credits and net actuarial loss, Tax (Provision) Benefit		(72)	(71)	(156)	(134)
Equity in Telesat-related other comprehensive income (loss), Tax (Provision) Benefit		(1)	6	1	(6)
Other comprehensive income, Tax (Provision) Benefit		(73)	(65)	(155)	(140)
Amortization of prior service credits and net actuarial gain (loss), Net-of-Tax Amount		269	269	584	508
Equity in Telesat-related other comprehensive income (loss), Net-of-Tax Amount		(2,054)	(17,448)	(4,185)	13,603
Other comprehensive income (loss), Net-of-tax Amount		$ (1,785)	$ (17,179)	$ (3,601)	$ 14,111

[1] Reclassifications are included in other expense.