Comprehensive Income Other Comprehensive Income (Details) - USD ($) $ in Thousands		3 Months Ended
		Mar. 31, 2017		Mar. 31, 2016
Schedule of Comprehensive Income [Line Items]
Other Comprehensive Income, before Tax		$ 252		$ 4,173
Other Comprehensive Income, Tax		(98)		(1,637)
Other Comprehensive Income	[1]	154		2,536
Unrealized Gains and Losses on Available for Sale Securities
Schedule of Comprehensive Income [Line Items]
Other Comprehensive Income Loss Before Reclassifications Before Tax		77		4,010
Other Comprehensive Income Loss Before Reclassifications Tax (Expense) Benefit		(30)		(1,573)
Net Unrealized Securities Holding Gains Arising During the Period		47		2,437
Amounts reclassified from accumulated other comprehensive income		0	[1]	0	[2]
Other Comprehensive Income	[2]	47		2,437
Amortization of Net Retirement Plan Actuarial Loss
Schedule of Comprehensive Income [Line Items]
Net Unrealized Securities Holding Gains Arising During the Period	[2]	0		0
Reclassification From Accumulated Other Comprehensive Income Current Period Before Tax		178		166
Reclassification From Accumulated Other Comprehensive Income Current Period Tax (Expense) Benefit		(69)		(65)
Amounts reclassified from accumulated other comprehensive income		109		101
Other Comprehensive Income	[2]	109		101
Accretion of Net Retirement Plan Prior Service Credit
Schedule of Comprehensive Income [Line Items]
Net Unrealized Securities Holding Gains Arising During the Period	[2]	0		0
Reclassification From Accumulated Other Comprehensive Income Current Period Before Tax		(3)		(3)
Reclassification From Accumulated Other Comprehensive Income Current Period Tax (Expense) Benefit		1		1
Amounts reclassified from accumulated other comprehensive income		(2)		(2)
Other Comprehensive Income	[2]	$ (2)		$ (2)

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

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