Comprehensive Income Changes in Accumulated Other Comprehensive Income By Component (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		6 Months Ended
	Jun. 30, 2013	Jun. 30, 2012	Jun. 30, 2013	Jun. 30, 2012
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (8,324)	$ (6,872)	$ (8,462)	$ (6,695)
Other comprehensive income (loss), before reclassifications, net of tax	(3,643)	445	(3,423)	347
Reclassification from Accumulated Other Comprehensive Income, current period, net of tax	228	138	146	59
Other Comprehensive (Loss) Income	(3,415)	583	(3,277)	406
Accumulated Other Comprehensive Income (Loss), Net of Tax	(11,739)	(6,289)	(11,739)	(6,289)
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	5,527	6,407	5,625	6,808
Other comprehensive income (loss), before reclassifications, net of tax	(3,643)	445	(3,423)	347
Reclassification from Accumulated Other Comprehensive Income, current period, net of tax	(8)	(86)	(326)	(389)
Other Comprehensive (Loss) Income	(3,651)	359	(3,749)	(42)
Accumulated Other Comprehensive Income (Loss), Net of Tax	1,876	6,766	1,876	6,766
Amortization of Net Retirement Plan Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Roll Forward]
Accumulated Other Comprehensive Income (Loss), Net of Tax	(13,800)	(13,481)	(14,036)	(13,709)
Other comprehensive income (loss), before reclassifications, net of tax	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income, current period, net of tax	236	229	472	457
Other Comprehensive (Loss) Income	236	229	472	457
Accumulated Other Comprehensive Income (Loss), Net of Tax	(13,564)	(13,252)	(13,564)	(13,252)
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)	202	(51)	206
Other comprehensive income (loss), before reclassifications, net of tax	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income, current period, net of tax	0	(5)	0	(9)
Other Comprehensive (Loss) Income	0	(5)	0	(9)
Accumulated Other Comprehensive Income (Loss), Net of Tax	$ (51)	$ 197	$ (51)	$ 197