Summary of Significant Accounting Policies - Basic and diluted earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended				6 Months Ended
	Jun. 30, 2022	Mar. 31, 2022	Jun. 30, 2021	Mar. 31, 2021	Jun. 30, 2022	Jun. 30, 2021
Numerator:
Net income	$ 3,823	$ 1,204	$ 3,253	$ 758	$ 5,027	$ 4,011
Less: Income allocated to unvested participating securities	65		35		85	43
Net income available to common stockholders	$ 3,758		$ 3,218		$ 4,942	$ 3,968
Denominator:
Denominator for basic earnings per share - weighted average shares	5,952		5,917		5,950	5,915
Effect of dilutive securities:
Common stock equivalents	0		0		0	0
Denominator for diluted earnings per share - adjusted weighted-average shares and assumed conversions	5,952		5,917		5,950	5,915
Basic earnings per share
Basic	$ 0.63		$ 0.54		$ 0.83	$ 0.67
Diluted earnings per share
Diluted earning per share	$ 0.63		$ 0.54		$ 0.83	$ 0.67