Cash and cash equivalents (Details) - USD ($) $ in Thousands |
Dec. 31, 2020 |
Dec. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|---|---|
| Cash and cash equivalents [abstract] | ||||
| Cash at bank and on hand - non restricted | $ 588,690 | $ 223,867 | ||
| Cash at bank and on hand - restricted | 279,811 | 338,928 | ||
| Cash and cash equivalents | 868,501 | 562,795 | $ 631,542 | $ 669,387 |
| U.S. Dollar [Member] | ||||
| Cash and cash equivalents [abstract] | ||||
| Cash and cash equivalents | 575,567 | 313,678 | ||
| Euro [Member] | ||||
| Cash and cash equivalents [abstract] | ||||
| Cash and cash equivalents | 196,431 | 181,961 | ||
| South African Rand [Member] | ||||
| Cash and cash equivalents [abstract] | ||||
| Cash and cash equivalents | 40,561 | 47,679 | ||
| Mexico, Peso [Member] | ||||
| Cash and cash equivalents [abstract] | ||||
| Cash and cash equivalents | 23,570 | 64 | ||
| Algerian Dinar [Member] | ||||
| Cash and cash equivalents [abstract] | ||||
| Cash and cash equivalents | 21,114 | 9,301 | ||
| Others [Member] | ||||
| Cash and cash equivalents [abstract] | ||||
| Cash and cash equivalents | $ 11,258 | $ 10,176 |