Clients and other receivable (Details) - USD ($) $ in Thousands |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|
| Clients and other receivables [Abstract] | ||
| Trade receivables | $ 163,856 | $ 186,728 |
| Tax receivables | 54,959 | 39,607 |
| Prepayments | 5,521 | 6,375 |
| Other accounts receivable | 12,059 | 11,739 |
| Clients and other receivables | 236,395 | 244,449 |
| Up to 3 Months [Member] | ||
| Clients and other receivables [Abstract] | ||
| Trade receivables | 163,856 | 186,728 |
| Euros [Member] | ||
| Clients and other receivables [Abstract] | ||
| Trade receivables | 91,303 | 109,165 |
| Rand [Member] | ||
| Clients and other receivables [Abstract] | ||
| Trade receivables | 25,193 | 23,792 |
| Other [Member] | ||
| Clients and other receivables [Abstract] | ||
| Trade receivables | 9,884 | 7,363 |
| All Foreign Currencies [Member] | ||
| Clients and other receivables [Abstract] | ||
| Trade receivables | $ 126,380 | $ 140,320 |