Net Income per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ 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, 2017	Sep. 30, 2017	Jun. 30, 2017	Mar. 31, 2017	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Earnings Per Share [Abstract]
Net income	$ 6,120	$ 5,959	$ 5,834	$ 5,740	$ 5,803	$ 5,490	$ 5,397	$ 5,229	$ 2,500	$ 3,757	$ 3,444	$ 3,192	$ 23,653	$ 21,919	$ 12,893
Weighted average common shares outstanding - Basic (in shares)													10,845	10,726	10,558
Plus: Potential dilutive common stock equivalents (in shares)													184	190	191
Weighted average common shares outstanding - Diluted (in shares)													11,029	10,916	10,749
Net income per common share - Basic (in dollars per share)	$ 0.56	$ 0.55	$ 0.54	$ 0.53	$ 0.54	$ 0.51	$ 0.50	$ 0.49	$ 0.23	$ 0.36	$ 0.33	$ 0.30	$ 2.18	$ 2.04	$ 1.22
Net income per common share - Diluted (in dollars per share)	$ 0.55	$ 0.54	$ 0.53	$ 0.52	$ 0.53	$ 0.50	$ 0.49	$ 0.48	$ 0.23	$ 0.35	$ 0.32	$ 0.30	$ 2.14	$ 2.01	$ 1.20
Stock options and common stock excluded from the income per share calculation as their effect would have been anti-dilutive (in shares)													243	109	71