Accumulated Other Comprehensive Income (Loss) (Reclassification adjustments) (Details) - USD ($) $ in Thousands	3 Months Ended	12 Months Ended
	Mar. 31, 2012	Dec. 31, 2015	Dec. 31, 2014	Dec. 31, 2013
Reclassification out of Accumulated Other Comprehensive Income [Line Items]
Net gains (losses) on sale of AFS securities		$ 163	$ 97	$ 171
Net AFS Impairment Loss	$ (282)
Income before federal income tax expense		18,418	16,068	14,706
Compensation and benefits		19,068	18,502	17,807
Federal income tax expense		3,288	2,344	2,196
NET INCOME		15,130	13,724	12,510
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		163	97	171
Federal income tax expense		55	33	58
NET INCOME		108	64	113
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		492	300	208
Federal income tax expense		167	102	71
NET INCOME		$ 325	$ 198	$ 137