Comprehensive Income Changes in Accumulated Other Comprehensive Income By Component (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (8,462)	$ (6,695)
Other comprehensive income (loss), before reclassifications, net of tax	220	(98)
Reclassification from Accumulated Other Comprehensive Income, current period, net of tax	(82)	(79)
Other Comprehensive (Loss) Income	138	(177)
Accumulated Other Comprehensive Income (Loss), Net of Tax	(8,324)	(6,872)
Unrealized Gains and Losses on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	5,625	6,808
Other comprehensive income (loss), before reclassifications, net of tax	220	(98)
Reclassification from Accumulated Other Comprehensive Income, current period, net of tax	(318)	(303)
Other Comprehensive (Loss) Income	(98)	(401)
Accumulated Other Comprehensive Income (Loss), Net of Tax	5,527	6,407
Amortization of Net Retirement Plan Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(14,036)	(13,709)
Other comprehensive income (loss), before reclassifications, net of tax	0	0
Reclassification from Accumulated Other Comprehensive Income, current period, net of tax	236	228
Other Comprehensive (Loss) Income	236	228
Accumulated Other Comprehensive Income (Loss), Net of Tax	(13,800)	(13,481)
Accretion of Net Retirement Plan Prior Service Credit [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(51)	206
Other comprehensive income (loss), before reclassifications, net of tax	0	0
Reclassification from Accumulated Other Comprehensive Income, current period, net of tax	0	(4)
Other Comprehensive (Loss) Income	0	(4)
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (51)	$ 202