Comprehensive Income Changes in Accumulated Other Comprehensive Income By Component (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014	Mar. 31, 2015	Dec. 31, 2014	Mar. 31, 2014	Dec. 31, 2013
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	$ (7,171)	$ (3,489)	$ (7,171)	$ (3,489)	$ (6,256)	$ (7,166)	$ (4,075)	$ (4,373)
Other comprehensive income, before reclassifications, net of tax	[1]	(1,014)	514	(159)	755
Reclassification from Accumulated Other Comprehensive Income, net of tax	[1]	99	72	154	129
Other Comprehensive Income	[1]	(915)	586	(5)	884
Unrealized Gains and Losses on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	2,315	3,145	2,315	3,145	3,339	2,539	2,615	2,374
Other comprehensive income, before reclassifications, net of tax		(1,014)	514	(159)	755
Reclassification from Accumulated Other Comprehensive Income, net of tax		(10)	16	(65)	16
Other Comprehensive Income	[1]	(1,024)	530	(224)	771
Amortization of Net Retirement Plan Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	(9,020)	(6,558)	(9,020)	(6,558)	(9,138)	(9,255)	(6,627)	(6,697)
Other comprehensive income, before reclassifications, net of tax	[1]	0	0	0	0
Reclassification from Accumulated Other Comprehensive Income, net of tax		118	69	235	139
Other Comprehensive Income	[1]	118	69	235	139
Accretion of Net Retirement Plan Prior Service Credit [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	(466)	(76)	(466)	(76)	$ (457)	$ (450)	$ (63)	$ (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)	(16)	(26)
Other Comprehensive Income	[1]	$ (9)	$ (13)	$ (16)	$ (26)

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