Comprehensive Income Changes in Accumulated Other Comprehensive Income By Component (Details) - USD ($) $ in Thousands		3 Months Ended		6 Months Ended
		Jun. 30, 2016	Jun. 30, 2015	Jun. 30, 2016		Jun. 30, 2015	Mar. 31, 2016	Dec. 31, 2015	Mar. 31, 2015	Dec. 31, 2014
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	$ (4,742)	$ (7,171)	$ (4,742)		$ (7,171)	$ (5,436)	$ (7,972)	$ (6,256)	$ (7,166)
Other comprehensive income, before reclassifications, net of tax	[1]	682	(1,014)	3,119		(159)
Reclassification from Accumulated Other Comprehensive Income, net of tax	[1]	12	99	111		154
Other Comprehensive Income	[1],[2]	694	(915)	3,230		(5)
Unrealized Gains and Losses on Available for Sale Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	3,660	2,315	3,660		2,315	3,066	629	3,339	2,539
Other comprehensive income, before reclassifications, net of tax	[1]	682	(1,014)	3,119	[2]	(159)
Reclassification from Accumulated Other Comprehensive Income, net of tax	[1]	(88)	(10)	(88)	[2]	(65)
Other Comprehensive Income	[1]	594	(1,024)	3,031		(224)
Amortization of Net Retirement Plan Actuarial Loss [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	(7,690)	(9,020)	(7,690)		(9,020)	(7,792)	(7,893)	(9,138)	(9,255)
Other comprehensive income, before reclassifications, net of tax	[1]	0	0	0		0
Reclassification from Accumulated Other Comprehensive Income, net of tax	[1]	102	118	203	[2]	235
Other Comprehensive Income	[1]	102	118	203		235
Accretion of Net Retirement Plan Prior Service Credit [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Accumulated Other Comprehensive Loss	[1]	(712)	(466)	(712)		(466)	$ (710)	$ (708)	$ (457)	$ (450)
Other comprehensive income, before reclassifications, net of tax	[1]	0	0	0		0
Reclassification from Accumulated Other Comprehensive Income, net of tax	[1]	(2)	(9)	(4)	[2]	(16)
Other Comprehensive Income	[1]	$ (2)	$ (9)	$ (4)		$ (16)

[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.