Accumulated Other Comprehensive Income (Loss) (Components of Accumulated Other Comprehensive Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		12 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Accumulated other comprehensive income (loss), beginning balance	$ (28,698)
Net current-period other comprehensive income (loss)	9,159	$ 234
Accumulated other comprehensive income (loss), ending balance	(19,539)		$ (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)	$ 127		788
Net current-period other comprehensive income (loss)	127		523
Accumulated other comprehensive income (loss), ending balance	(13,332)		(13,459)
Proportionate Share of Telesat Other Comprehensive Loss [Member]
Accumulated other comprehensive income (loss), beginning balance	(15,239)	(15,239)	$ (15,239)
Other comprehensive income (loss) before reclassification	$ 9,032
Amounts reclassified from accumulated other comprehensive income (loss)
Net current-period other comprehensive income (loss)	$ 9,032
Accumulated other comprehensive income (loss), ending balance	(6,207)		$ (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	9,032		(265)
Amounts reclassified from accumulated other comprehensive income (loss)	127		788
Net current-period other comprehensive income (loss)	9,159		523
Accumulated other comprehensive income (loss), ending balance	$ (19,539)		$ (28,698)