Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income and Related Tax Effects) (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Accumulated Other Comprehensive Loss [Abstract]
Amortization of prior service credits and net actuarial loss, Before-Tax Amount	[1]	$ 370	$ 321	$ 1,110	$ 963
Equity in Telesat-related other comprehensive income (loss), Before-Tax Amount		8,052	(7,477)	3,866	6,132
Other comprehensive income (loss), Before-Tax Amount		8,422	(7,156)	4,976	7,095
Amortization of prior service credits and net actuarial loss, Tax (Provision) Benefit		(76)	(68)	(232)	(202)
Equity in Telesat-related other comprehensive income (loss), Tax (Provision) Benefit		(3)	4	(2)	(2)
Other comprehensive income, Tax (Provision) Benefit		(79)	(64)	(234)	(204)
Amortization of prior service credits and net actuarial gain (loss), Net-of-Tax Amount		294	253	878	761
Equity in Telesat-related other comprehensive income (loss), Net-of-Tax Amount		8,049	(7,473)	3,864	6,130
Other comprehensive income (loss), Net-of-tax Amount		$ 8,343	$ (7,220)	$ 4,742	$ 6,891

[1] Reclassifications are included in other expense.