Summary of Significant Accounting Policies - Basic and diluted earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended						9 Months Ended
	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Sep. 30, 2022	Sep. 30, 2021
Numerator:
Net (loss) income	$ (104)	$ 3,823	$ 1,204	$ 3,454	$ 3,253	$ 758	$ 4,923	$ 7,465
Less: Income allocated to unvested participating securities	(1)			37			37	80
Net income available to common stockholders	$ (103)			$ 3,417			$ 4,886	$ 7,385
Denominator:
Denominator for basic earnings per share - weighted average shares	5,961			5,917			5,977	5,916
Effect of dilutive securities:
Common stock equivalents	0			0			0	0
Denominator for diluted earnings per share - adjusted weighted-average shares and assumed conversions	5,961			5,917			5,977	5,916
Basic earnings (loss) per share
Basic earnings (loss) per share	$ (0.01)			$ 0.58			$ 0.82	$ 1.25
Diluted earnings (loss) per share
Diluted earnings (loss) per share	$ (0.01)			$ 0.58			$ 0.82	$ 1.25