Other Comprehensive Income (Schedule of Changes in Accumulated Other Comprehensive Income by Component) (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	$ (105,267)		$ (145,310)
Other Comprehensive Income (Loss), before Reclassifications	(3,963)		43
Amounts reclassified from accumulated other comprehensive income (loss)	16,715		52,752
Other comprehensive income (loss)	12,752	10,826	52,795	35,758
Accumulated Other Comprehensive Income (Loss), Ending Balance	(92,515)		(92,515)
Change in Fair Value of Interest Rate Swaps [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(79,473)		(116,382)
Other Comprehensive Income (Loss), before Reclassifications	(5,134)		(2,798)
Amounts reclassified from accumulated other comprehensive income (loss)	15,984		50,557
Other comprehensive income (loss)	10,850		47,759
Accumulated Other Comprehensive Income (Loss), Ending Balance	(68,623)		(68,623)
Change in Fair Value of Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	6,258		4,588
Other Comprehensive Income (Loss), before Reclassifications	1,171		2,841
Other comprehensive income (loss)	1,171		2,841
Accumulated Other Comprehensive Income (Loss), Ending Balance	7,429		7,429
Change in Unrecognized Pension Cost Components [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Income (Loss), Beginning Balance	(32,052)		(33,516)
Amounts reclassified from accumulated other comprehensive income (loss)	731		2,195
Other comprehensive income (loss)	731		2,195
Accumulated Other Comprehensive Income (Loss), Ending Balance	$ (31,321)		$ (31,321)