Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Accumulated other comprehensive income (loss), beginning balance	$ (28,698)
Net current-period other comprehensive income (loss)	14,862	$ 523	$ (8,305)
Accumulated other comprehensive income (loss), ending balance	(13,836)	(28,698)
Postretirement Benefits [Member]
Accumulated other comprehensive income (loss), beginning balance	(13,459)	(13,982)	(9,171)
Other comprehensive income (loss) before reclassification	(1,209)	(265)	(5,147)
Amounts reclassified from accumulated other comprehensive income (loss)	594	788	336
Net current-period other comprehensive income (loss)	(615)	523	(4,811)
Accumulated other comprehensive income (loss), ending balance	(14,074)	(13,459)	(13,982)
Proportionate Share of Telesat Other Comprehensive Loss [Member]
Accumulated other comprehensive income (loss), beginning balance	(15,239)	(15,239)	(11,745)
Other comprehensive income (loss) before reclassification	15,477		(3,494)
Net current-period other comprehensive income (loss)	15,477		(3,494)
Accumulated other comprehensive income (loss), ending balance	238	(15,239)	(15,239)
Accumulated Other Comprehensive Loss [Member]
Accumulated other comprehensive income (loss), beginning balance	(28,698)	(29,221)	(20,916)
Other comprehensive income (loss) before reclassification	14,268	(265)	(8,641)
Amounts reclassified from accumulated other comprehensive income (loss)	594	788	336
Net current-period other comprehensive income (loss)	14,862	523	(8,305)
Accumulated other comprehensive income (loss), ending balance	$ (13,836)	$ (28,698)	$ (29,221)