Project debt, Movement in project debt and Significant foreign currency denominated debts (Details) - USD ($) $ in Thousands |
Dec. 31, 2017 |
Dec. 31, 2016 |
Dec. 31, 2015 |
|---|---|---|---|
| Project Debt [Abstract] | |||
| Project debt | $ 5,475,208 | $ 5,330,467 | $ 5,470,669 |
| Euro [Member] | |||
| Project Debt [Abstract] | |||
| Project debt | 2,286,771 | 2,102,985 | |
| Algerian Dinar [Member] | |||
| Project Debt [Abstract] | |||
| Project debt | 35,093 | 41,598 | |
| Rand [Member] | |||
| Project Debt [Abstract] | |||
| Project debt | 456,179 | 419,708 | |
| All Foreign Currencies [Member] | |||
| Project Debt [Abstract] | |||
| Project debt | $ 2,778,043 | $ 2,564,291 |