Consolidated Statements of Comprehensive Income (Unaudited) - USD ($) $ in Thousands	3 Months Ended				9 Months Ended
	Sep. 30, 2017		Sep. 30, 2016		Sep. 30, 2017		Sep. 30, 2016
Statement of Comprehensive Income [Abstract]
Net Income	$ 7,416		$ 6,738		$ 21,255		$ 19,934
Other Comprehensive Income (Loss), Net of Tax [Abstract]
Net Unrealized Securities Holding Gains (Losses) Arising During the Period	9	[1]	(810)	[1]	465		2,309	[1]
Reclassification Adjustments for Securities Gains Included in Net Income	(6)	[1]	0	[1]	(6)	[2]	(88)	[1]
Amortization of Net Retirement Plan Actuarial Loss	64	[1]	111	[1]	245		314	[1]
Accretion of Net Retirement Plan Prior Service Credit	(2)	[1]	(1)	[1]	(5)		(5)	[1]
Other Comprehensive Income (Loss)	65		(700)		699		2,530
Comprehensive Income	$ 7,481		$ 6,038		$ 21,954		$ 22,464

[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.