Trade and other receivables (Details) - USD ($) $ in Thousands |
Dec. 31, 2020 |
Dec. 31, 2019 |
|---|---|---|
| Trade and other receivables [Abstract] | ||
| Trade receivables | $ 258,087 | $ 242,008 |
| Tax receivables | 50,663 | 50,901 |
| Prepayments | 12,074 | 5,150 |
| Other accounts receivable | 10,911 | 19,508 |
| Trade and other receivables | 331,735 | 317,568 |
| Euros [Member] | ||
| Trade and other receivables [Abstract] | ||
| Trade receivables | 105,826 | 108,280 |
| South African Rand [Member] | ||
| Trade and other receivables [Abstract] | ||
| Trade receivables | 24,121 | 24,289 |
| Other [Member] | ||
| Trade and other receivables [Abstract] | ||
| Trade receivables | 6,929 | 4,001 |
| All Foreign Currencies [Member] | ||
| Trade and other receivables [Abstract] | ||
| Trade receivables | $ 136,876 | $ 136,570 |