Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	12 Months Ended
	Dec. 31, 2013		Dec. 31, 2012		Dec. 31, 2011
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ (45,379)	[1]
Other comprehensive income before reclassifications	24,537	[1]
Amounts reclassified from accumulated other comprehensive income	(339)	[1]
Other comprehensive income (loss)	24,198	[1]	(2,289)		(14,291)
Ending balance	(21,181)	[1]	(45,379)	[1]
Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(902)	[1]
Other comprehensive income before reclassifications	265	[1]
Amounts reclassified from accumulated other comprehensive income	0	[1]
Other comprehensive income (loss)	265	[1]
Ending balance	(637)	[1]
Investment in Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	2,569	[1]
Other comprehensive income before reclassifications	5,292	[1]
Amounts reclassified from accumulated other comprehensive income	0	[1]
Other comprehensive income (loss)	5,292	[1]
Ending balance	7,861	[1]
Defined Benefit Plan Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(47,046)	[1]
Other comprehensive income before reclassifications	18,980	[1]
Amounts reclassified from accumulated other comprehensive income	(339)	[1]
Other comprehensive income (loss)	18,641	[1]
Ending balance	$ (28,405)	[1]

[1] All amounts are net of tax. Amounts in parentheses indicate debits