Accumulated Other Comprehensive Income (Loss) (Reclassification adjustments) (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net gains (losses) on sale of AFS securities	$ 142	$ 245	$ 163
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount	0	770	0
Net AFS Impairment Loss	0	(770)	0
Income before federal income tax expense	16,253	16,147	18,418
Compensation and benefits	21,525	19,170	18,431
Federal income tax expense	(3,016)	(2,348)	(3,288)
NET INCOME	13,237	13,799	15,130
Reclassification out of Accumulated Other Comprehensive Income [Member] | Unrealized Holding Gains (Losses) on AFS Securities [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net gains (losses) on sale of AFS securities	142	245	163
Marketable Securities, Realized Loss, Other than Temporary Impairments, Amount	0	(770)	0
Marketable Securities, Realized Gain (Loss)	142	(525)	163
Federal income tax expense	(48)	179	(55)
NET INCOME	94	(346)	108
Reclassification out of Accumulated Other Comprehensive Income [Member] | Defined Benefit Pension Plan [Member]
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Compensation and benefits	412	238	492
Federal income tax expense	(140)	(81)	(167)
NET INCOME	$ 272	$ 157	$ 325