Earnings Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2019	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Dec. 31, 2018	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Dec. 31, 2019	Dec. 31, 2018
Earnings Per Share
Net income	$ 5,045	$ 5,366	$ 5,060	$ 6,524	$ 4,643	$ 4,786	$ 4,963	$ 4,820	$ 21,995	$ 19,212
Income allotted to participating securities									(149)	(90)
Net income available to common shareholders									$ 21,846	$ 19,122
Weighted-average number of shares used in:
Basic earnings per share (in shares)									9,196,674	9,219,123
Dilutive common stock equivalents:
Stock options and restricted stock units (in shares)									128,940	181,272
Diluted earnings per share (in shares)									9,325,614	9,400,395
Net income per common share, basic (in dollars per share)	$ 0.54	$ 0.58	$ 0.55	$ 0.71	$ 0.50	$ 0.52	$ 0.54	$ 0.52	$ 2.38	$ 2.07
Net income per common share, diluted (in dollars per share)	$ 0.53	$ 0.57	$ 0.54	$ 0.70	$ 0.50	$ 0.51	$ 0.53	$ 0.51	$ 2.34	$ 2.03