Summary of Significant Accounting Policies - Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018
Numerator:
Net income	$ 4,103	$ 4,835
Denominator:
Weighted average common shares (in shares)	5,096,000	5,351,000
Dilutive potential common shares (in shares)	31,000	49,000
Weighted average fully diluted shares (in shares)	5,127,000	5,400,000
Earnings per share:
Basic (in dollars per share)	$ 0.81	$ 0.90
Diluted (in dollars per share)	$ 0.80	$ 0.90
Outstanding common stock equivalents having no dilutive effect (in shares)	0	0