Summary of Significant Accounting Policies - Basic and diluted earnings per share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2022	Sep. 30, 2022	Jun. 30, 2022	Mar. 31, 2022	Dec. 31, 2021	Sep. 30, 2021	Jun. 30, 2021	Mar. 31, 2021	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Numerator:
Net income									$ 9,202	$ 11,157	$ (1,913)
Less: Income allocated to unvested participating securities									140	190	(21)
Net income available to common stockholders									$ 9,062	$ 10,967	$ (1,892)
Denominator:
Denominator for basic earnings per share - weighted average shares	6,013	5,961	5,952	5,948	5,922	5,917	5,917	5,913	5,973	5,917	5,871
Effect of dilutive securities:
Denominator for diluted earnings per share - adjusted weighted-average shares and assumed conversions	6,013	5,961	5,952	5,948	5,922	5,917	5,917	5,913	5,973	5,917	5,871
Earnings per share:
Basic earnings (loss) per share	$ 0.70	$ (0.01)	$ 0.63	$ 0.20	$ 0.60	$ 0.58	$ 0.54	$ 0.13	$ 1.52	$ 1.85	$ (0.32)
Diluted earnings (loss) per share
Diluted earnings (loss) per share	$ 0.70	$ (0.01)	$ 0.63	$ 0.20	$ 0.60	$ 0.58	$ 0.54	$ 0.13	$ 1.52	$ 1.85	$ (0.32)