Nature of business (Details) $ in Millions |
3 Months Ended | |
|---|---|---|
|
Mar. 31, 2016
USD ($)
state
project
item
MW
|
Dec. 31, 2015
USD ($)
|
|
| Nature of business | ||
| Gross generating capacity of project (in MW) | MW | 2,138 | |
| Ownership interest in operational power generation projects (in MW) | MW | 1,500 | |
| Number of operational power generation projects | project | 23 | |
| Number of states in which power generation projects operate | state | 11 | |
| Number of provinces in which power generation projects operate | item | 2 | |
| Number of projects which are wholly owned | project | 18 | |
| Recent accounting pronouncements adopted | ||
| Deferred financing costs | $ | $ 39.5 | $ 42.5 |