Project debt, Repayment schedule (Details) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|---|
| Repayment schedule [Abstract] | |||
| Project debt | $ 5,475,208 | $ 5,330,467 | $ 5,470,669 |
| 2018 [Member] | |||
| Repayment schedule [Abstract] | |||
| Interest repayment | 21,612 | ||
| Nominal repayment | 224,679 | ||
| 2019 [Member] | |||
| Repayment schedule [Abstract] | |||
| Project debt | 246,471 | ||
| 2020 [Member] | |||
| Repayment schedule [Abstract] | |||
| Project debt | 265,002 | ||
| 2021 [Member] | |||
| Repayment schedule [Abstract] | |||
| Project debt | 280,303 | ||
| 2022 [Member] | |||
| Repayment schedule [Abstract] | |||
| Project debt | 313,559 | ||
| Subsequent Years [Member] | |||
| Repayment schedule [Abstract] | |||
| Project debt | $ 4,123,582 |