Accounting policies - Revenue recognized and billed on services (Details) - USD ($)	3 Months Ended	12 Months Ended
	Mar. 31, 2023	Dec. 31, 2022
Accounting policies
Revenue recognized to date on contracts in progress	$ 36,464,115	$ 25,469,014
Amounts billed to date on contracts in progress	(49,204,112)	(33,407,182)
Retainage	3,368,424	2,047,969
Net contract asset	(9,371,573)	(5,890,199)
Contract assets	6,127,587	2,913,722
Contract liabilities	(15,499,160)	(8,803,921)
Net contract liability	$ (9,371,573)	$ (5,890,199)