Intangible assets (Details) - USD ($)	Dec. 31, 2018	Dec. 31, 2017
Cost
Finite-Lived Intangible Assets, Gross	$ 5,900,000	$ 5,900,000
Accumulated amortization
Finite-Lived Intangible Assets, Accumulated Amortization	(4,008,333)	(2,668,333)
Intangible assets, net	1,891,667	3,231,667
Non-compete agreement
Cost
Finite-Lived Intangible Assets, Gross	400,000	400,000
Accumulated amortization
Finite-Lived Intangible Assets, Accumulated Amortization	(233,333)	(153,333)
Trade name
Cost
Finite-Lived Intangible Assets, Gross	1,400,000	1,400,000
Accumulated amortization
Finite-Lived Intangible Assets, Accumulated Amortization	(272,222)	(178,889)
Certifications/programs
Cost
Finite-Lived Intangible Assets, Gross	2,000,000	2,000,000
Accumulated amortization
Finite-Lived Intangible Assets, Accumulated Amortization	(1,944,444)	(1,277,778)
Customer backlog
Cost
Finite-Lived Intangible Assets, Gross	100,000	100,000
Accumulated amortization
Finite-Lived Intangible Assets, Accumulated Amortization	(100,000)	(100,000)
Customer relationships
Cost
Finite-Lived Intangible Assets, Gross	2,000,000	2,000,000
Accumulated amortization
Finite-Lived Intangible Assets, Accumulated Amortization	$ (1,458,334)	$ (958,333)