Accumulated Other Comprehensive Income (Components Of Accumulated Other Comprehensive Loss) (Details) (USD $)	3 Months Ended			12 Months Ended
	Mar. 31, 2013		Mar. 31, 2012	Dec. 31, 2012	Dec. 31, 2011
Derivatives, Balance					$ (1,306,000)
Unrealized Gains (Losses) on Investments, Balance					580,000
Postretirement Benefits, Balance	(16,725,000)			(17,653,000)	(132,695,000)
Proportionate Share Of Telesat Other Comprehensive Loss, Balance	(19,297,000)			(19,741,000)	(21,054,000)
Accumulated Other Comprehensive Loss, Balance	(36,022,000)			(37,394,000)	(154,475,000)
Derivatives, Other comprehensive income before reclassification			(1,002,000)	(415,000)
Unrealized Gains (Losses) on Investments, Other comprehensive income before reclassification			94,000	(120,000)
Postretirement Benefits, Other comprehensive income before reclassification				1,668,000
Proportionate Share of Telesat Other Comprehensive Loss, Other comprehensive income before reclassification	444,000			1,313,000
Accumulated Other Comprehensive Loss, Other comprehensive income before reclassification	444,000			2,446,000
Derivatives, Amounts reclassified from accumulated other comprehensive income			1,958,000	1,721,000
Unrealized Gains (losses) on Investments, Amounts reclassified from accumulated other comprehensive income				(460,000)
Postretirement Benefits, Amount reclassified from accumulated other comprehensive income	928,000	[1]	1,204,000	113,374,000
Accumulated Other Comprehensive Loss, Amounts reclassified from accumulated other comprehensive income	928,000			114,635,000
Derivatives, Net current-period other comprehensive income			956,000	1,306,000
Unrealized Gains (Losses) on Investments, Net current-period other comprehensive income				(580,000)
Postretirement Benefits, Net current-period other comprehensive income	928,000			115,042,000
Proportionate Share Of Telesat Other Comprehensive Loss, Net current period comprehensive income	444,000			1,313,000
Accumulated Other Comprehensive Loss, Net current-period other comprehensive income	1,372,000		2,797,000	117,081,000
General Administrative Expenses [Member]
Reclassification from postretirement benefits accumulated other comprehensive loss	1,500,000
Income Tax Provision Benefit [Member]
Reclassification from postretirement benefits accumulated other comprehensive loss	$ (600,000)

[1] Reclassification from postretirement benefits accumulated other comprehensive loss comprises $1.5 million included in general and administrative expenses and $0.6 million tax benefit thereon included in income tax provision in our condensed consolidated statement of operations.