Income taxes (Details) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2023	Sep. 30, 2022	Sep. 30, 2023	Sep. 30, 2022	Dec. 31, 2022
Income Taxes
Income tax expense (benefit)	$ 202,000	$ 185,000	$ 80,000	$ 557,000
Interest and penalties accrued	$ 0		$ 0		$ 0