Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income and Related Tax Effects) (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2021	Mar. 31, 2020
Accumulated Other Comprehensive Loss [Abstract]
Amortization of prior service credits and net actuarial loss, Before-Tax Amount	[1]	$ 399	$ 302
Equity in Telesat-related other comprehensive income (loss), Before-Tax Amount		(2,133)	31,063
Other comprehensive income (loss), Before-Tax Amount		(1,734)	31,365
Amortization of prior service credits and net actuarial loss, Tax (Provision) Benefit		(84)	(63)
Equity in Telesat-related other comprehensive income (loss), Tax (Provision) Benefit		2	(12)
Other comprehensive income, Tax (Provision) Benefit		(82)	(75)
Amortization of prior service credits and net actuarial gain (loss), Net-of-Tax Amount		315	239
Equity in Telesat-related other comprehensive income (loss), Net-of-Tax Amount		(2,131)	31,051
Other comprehensive income (loss), Net-of-tax Amount		$ (1,816)	$ 31,290

[1] Reclassifications are included in other expense.