Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended		12 Months Ended
	Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2016	Sep. 30, 2015	Dec. 31, 2015
Accumulated other comprehensive income (loss), beginning balance			$ (28,698)
Net current-period other comprehensive income (loss)	$ 1,713	$ (698)	11,289	$ 664
Accumulated other comprehensive income (loss), ending balance	(17,409)		(17,409)		$ (28,698)
Postretirement Benefits [Member]
Accumulated other comprehensive income (loss), beginning balance			(13,459)	(13,982)	(13,982)
Other comprehensive income (loss) before reclassification					(265)
Amounts reclassified from accumulated other comprehensive income (loss)			426		788
Net current-period other comprehensive income (loss)			426		523
Accumulated other comprehensive income (loss), ending balance	(13,033)		(13,033)		(13,459)
Proportionate Share of Telesat Other Comprehensive Income (Loss) [Member]
Accumulated other comprehensive income (loss), beginning balance			(15,239)	(15,239)	(15,239)
Other comprehensive income (loss) before reclassification			10,863
Amounts reclassified from accumulated other comprehensive income (loss)
Net current-period other comprehensive income (loss)			10,863
Accumulated other comprehensive income (loss), ending balance	(4,376)		(4,376)		(15,239)
Accumulated Other Comprehensive Loss [Member]
Accumulated other comprehensive income (loss), beginning balance			(28,698)	$ (29,221)	(29,221)
Other comprehensive income (loss) before reclassification			10,863		(265)
Amounts reclassified from accumulated other comprehensive income (loss)			426		788
Net current-period other comprehensive income (loss)			11,289		523
Accumulated other comprehensive income (loss), ending balance	$ (17,409)		$ (17,409)		$ (28,698)