Comprehensive Income Changes in Accumulated Other Comprehensive Income By Component (Details) - USD ($) $ in Thousands		3 Months Ended				9 Months Ended
		Sep. 30, 2016		Sep. 30, 2015		Sep. 30, 2016		Sep. 30, 2015		Jun. 30, 2016	Dec. 31, 2015	Jun. 30, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	$ (5,442)		$ (6,520)		$ (5,442)		$ (6,520)		$ (4,742)	$ (7,972)	$ (7,171)	$ (7,166)
Other comprehensive income, before reclassifications, net of tax	[1]	(810)		543		2,309		384
Reclassification from Accumulated Other Comprehensive Income, net of tax	[1]	110		108		221		262
Other Comprehensive Income	[1],[2]	(700)		651		2,530		646
Unrealized Gains and Losses on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	2,850		2,858		2,850		2,858		3,660	629	2,315	2,539
Other comprehensive income, before reclassifications, net of tax		(810)	[1]	543	[1]	2,309	[2]	384	[1]
Reclassification from Accumulated Other Comprehensive Income, net of tax		0	[1]	0	[1]	(88)	[2]	(65)	[1]
Other Comprehensive Income	[1]	(810)		543		2,221		319
Amortization of Net Retirement Plan Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	(7,579)		(8,903)		(7,579)		(8,903)		(7,690)	(7,893)	(9,020)	(9,255)
Other comprehensive income, before reclassifications, net of tax	[1]	0		0		0		0
Reclassification from Accumulated Other Comprehensive Income, net of tax		111	[1]	117	[1]	314	[2]	352	[1]
Other Comprehensive Income	[1]	111		117		314		352
Accretion of Net Retirement Plan Prior Service Credit [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	(713)		(475)		(713)		(475)		$ (712)	$ (708)	$ (466)	$ (450)
Other comprehensive income, before reclassifications, net of tax	[1]	0		0		0		0
Reclassification from Accumulated Other Comprehensive Income, net of tax		(1)	[1]	(9)	[1]	(5)	[2]	(25)	[1]
Other Comprehensive Income	[1]	$ (1)		$ (9)		$ (5)		$ (25)

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

[2] These accumulated other comprehensive income components are included in the computation of net periodic pension cost.