Summary of Significant Accounting Policies - Basic and diluted earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Numerator:
Net income	$ 1,204	$ 758
Less: Income (loss) allocated to unvested participating securities	20	8
Net income (loss) available to common stockholders	$ 1,184	$ 750
Denominator:
Weighted average common shares	5,948	5,913
Effect of dilutive securities:
Common stock equivalents	0	0
Denominator for diluted earnings per share - adjusted weighted-average shares and assumed conversions	5,948	5,913
Basic earnings (loss) per share
Basic	$ 0.20	$ 0.13
Diluted earnings (loss) per share
Diluted earning per share	$ 0.20	$ 0.13