| | 12-31-2017 | | 12-31-2016 | | 12-31-2015 | | |||
| | ThU.S.$ | | ThU.S.$ | | ThU.S.$ | | |||
Opening balance | | | (16,644) | | | (19,860) | | | (18,520) | |
Impairment losses recognized on receivables | | | (139) | | | (3,950) | | | (3,072) | |
Reversal of impairment losses | | | 2,282 | | | 7,166 | | | 1,732 | |
Closing balance | | | (14,501) | | | (16,644) | | | (19,860) | |