Comprehensive Income Changes in Accumulated Other Comprehensive Income By Component (Details) - USD ($) $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Jun. 30, 2015	Dec. 31, 2014	Jun. 30, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	$ (6,520)	$ (4,284)	$ (6,520)	$ (4,284)	$ (7,171)	$ (7,166)	$ (3,489)	$ (4,373)
Other comprehensive income, before reclassifications, net of tax	[1]	543	(770)	384	(15)
Reclassification from Accumulated Other Comprehensive Income, net of tax	[1]	108	(25)	262	104
Other Comprehensive Income	[1]	651	(795)	646	89
Unrealized Gains and Losses on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	2,858	2,293	2,858	2,293	2,315	2,539	3,145	2,374
Other comprehensive income, before reclassifications, net of tax		543	(770)	384	(15)
Reclassification from Accumulated Other Comprehensive Income, net of tax		0	(82)	(65)	(66)
Other Comprehensive Income	[1]	543	(852)	319	(81)
Amortization of Net Retirement Plan Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	(8,903)	(6,488)	(8,903)	(6,488)	(9,020)	(9,255)	(6,558)	(6,697)
Other comprehensive income, before reclassifications, net of tax	[1]	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income, net of tax		117	70	352	209
Other Comprehensive Income	[1]	117	70	352	209
Accretion of Net Retirement Plan Prior Service Credit [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	(475)	(89)	(475)	(89)	$ (466)	$ (450)	$ (76)	$ (50)
Other comprehensive income, before reclassifications, net of tax	[1]	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income, net of tax		(9)	(13)	(25)	(39)
Other Comprehensive Income	[1]	$ (9)	$ (13)	$ (25)	$ (39)

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