Consolidated Statement of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Net Income	$ 26,534	$ 24,662	$ 23,360
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	697	(1,208)	(2,961)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	441	402	168
Other Comprehensive Income (Loss)	1,138	(806)	(2,793)
Comprehensive Income	27,672	23,856	20,567
Accumulated Net Unrealized Investment Gain (Loss) [Member]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	(1,024)	(1,832)	232
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	13	(78)	(67)
Accumulated Defined Benefit Plans Adjustment, Net Unamortized Gain (Loss) [Member]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	1,721	848	(2,846)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	435	514	288
Accumulated Defined Benefit Plans Adjustment, Net Prior Service Cost (Credit) [Member]
Other Comprehensive Income (Loss), before Reclassifications, Net of Tax	0	(224)	(347)
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax	$ (7)	$ (34)	$ (53)