Accounting policies - Revenue recognized and billed on services (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2023	Dec. 31, 2022
Accounting policies
Revenue recognized to date on contracts in progress	$ 58,727,821	$ 25,469,014
Amounts billed to date on contracts in progress	(68,535,879)	(33,407,182)
Retainage	5,072,338	2,047,969
Net contract asset	(4,735,720)	(5,890,199)
Contract assets	8,192,770	2,913,722
Contract liabilities	(12,928,490)	(8,803,921)
Net contract liability	$ (4,735,720)	$ (5,890,199)