Nature of business (Details)	12 Months Ended
	Dec. 31, 2020 region state project MW
Nature of business
Number of states in which power generation projects operate | state	11
Number of provinces in which power generation projects operate | region	2
Number of power generation projects | project	21
Gross generating capacity of project (in MW) | MW	1,723
Ownership interest in power generation projects (in MW) | MW	1,327
Number of projects which are majority owned | project	16