Accumulated Other Comprehensive Income (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended				6 Months Ended
	Jun. 30, 2014		Jun. 30, 2013		Jun. 30, 2014		Jun. 30, 2013
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	$ (24,157)	[1]	$ (43,277)	[1]	$ (21,181)		$ (45,379)
Other comprehensive income before reclassifications	(2,781)	[1]	1,337	[1]	(5,672)		3,524
Amounts reclassified from accumulated other comprehensive income (loss)	(85)	[1]	(85)	[1]	(170)		(170)
Other comprehensive income (loss)	(2,866)	[1]	1,252	[1]	(5,842)		3,354
Ending balance	(27,023)	[1]	(42,025)	[1]	(27,023)	[1]	(42,025)	[1]
Losses on Cash Flow Hedges
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(568)	[1]	(872)	[1]	(637)		(902)
Other comprehensive income before reclassifications	62	[1]	108	[1]	131		138
Amounts reclassified from accumulated other comprehensive income (loss)	0	[1]	0	[1]	0		0
Other comprehensive income (loss)	62	[1]	108	[1]	131		138
Ending balance	(506)	[1]	(764)	[1]	(506)	[1]	(764)	[1]
Investment in Debt Securities
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	4,629	[1]	2,872	[1]	7,861		2,569
Other comprehensive income before reclassifications	(2,230)	[1]	0	[1]	(5,462)		303
Amounts reclassified from accumulated other comprehensive income (loss)	0	[1]	0	[1]	0		0
Other comprehensive income (loss)	(2,230)	[1]	0	[1]	(5,462)		303
Ending balance	2,399	[1]	2,872	[1]	2,399	[1]	2,872	[1]
Defined Benefit Plan Items
Accumulated Other Comprehensive Income (Loss), Net of Tax [Roll Forward]
Beginning Balance	(28,218)	[1]	(45,277)	[1]	(28,405)		(47,046)
Other comprehensive income before reclassifications	(613)	[1]	1,229	[1]	(341)		3,083
Amounts reclassified from accumulated other comprehensive income (loss)	(85)	[1]	(85)	[1]	(170)		(170)
Other comprehensive income (loss)	(698)	[1]	1,144	[1]	(511)		2,913
Ending balance	$ (28,916)	[1]	$ (44,133)	[1]	$ (28,916)	[1]	$ (44,133)	[1]

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