Accumulated Other Comprehensive Income (Loss) (Components of Other Comprehensive Income and Related Tax Effects) (Details) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2020	Dec. 31, 2019
Net actuarial gain (loss) and prior service credits, Before-Tax Amount		$ (4,877)	$ (2,921)
Amortization of prior service credits and net actuarial loss, Before-Tax Amount	[1]	1,299	1,008
Pension and other postretirement benefits, Before-Tax Amount		(3,578)	(1,913)
Equity in Telesat-related other comprehensive income (loss), Before-Tax Amount		(14,236)	(35,793)
Other comprehensive income (loss), Before-Tax Amount		(17,814)	(37,706)
Net actuarial gain (loss) and prior service credits, Tax (Provision) Benefit		1,025	614
Amortization of prior service credits and net actuarial loss, Tax (Provision) Benefit		(273)	(212)
Pension and other post retirement benefits, Tax (Provision) Benefit		752	402
Equity in Telesat-related other comprehensive income (loss), Tax (Provision) Benefit	[2]	4	10
Other comprehensive income, Tax (Provision) Benefit		756	412
Net actuarial gain (loss) and prior service credits, Net-of-Tax Amount		(3,852)	(2,307)
Amortization of prior service credits and net actuarial gain (loss), Net-of-Tax Amount		1,026	796
Pension and other postretirement benefits, Net-of-Tax Amount		(2,826)	(1,511)
Equity in Telesat-related other comprehensive income (loss), Net-of-Tax Amount		(14,232)	(35,783)
Other comprehensive income (loss), Net-of-tax Amount		$ (17,058)	$ (37,294)

[1] Reclassifications are included in other expenses.

[2] See Note 7, Income Taxes