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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Amortization of prior service credits and net actuarial loss, Before-Tax Amount	[1]	$ 251	$ 265	$ 752	$ 797
Proportionate share of Telesat Holdco other comprehensive income (loss), Before-Tax Amount		(1,519)	(7,115)	(7,859)	2,194
Other comprehensive income (loss), Before-Tax Amount		(16,214)	(6,850)	(29,163)	2,991
Amortization of prior service credits and net actuarial loss, Tax (Provision) Benefit		(52)	(56)	(158)	(168)
Proportionate share of Telesat Holdco other comprehensive income (loss), Tax (Provision) Benefit		1	1,496	2	(461)
Other comprehensive income, Tax (Provision) Benefit		(47)	1,440	(150)	(629)
Amortization of prior service credits and net actuarial gain (loss), Net-of-Tax Amount		199	209	594	629
Proportionate share of Telesat Holdco other comprehensive income (loss), Net-of-Tax Amount		(1,518)	(5,619)	(7,857)	1,733
Other comprehensive income (loss), Net-of-tax Amount		(16,261)	$ (5,410)	(29,313)	$ 2,362
Restatement Adjustment [Member]
Proportionate share of Telesat Holdco other comprehensive income (loss), Before-Tax Amount		(14,946)		(22,056)
Proportionate share of Telesat Holdco other comprehensive income (loss), Tax (Provision) Benefit		4		6
Proportionate share of Telesat Holdco other comprehensive income (loss), Net-of-Tax Amount		$ (14,942)		$ (22,050)

[1] Reclassifications are included in other expense.