ASSET RETIREMENT OBLIGATION (Details) - USD ($) $ in Thousands |
12 Months Ended | |
|---|---|---|
Dec. 31, 2017 |
Dec. 31, 2016 |
|
| Asset Retirement Obligation Disclosure [Abstract] | ||
| Period during which all related assets will be removed from calculation | 55 years | |
| Asset Retirement Obligation, Roll Forward Analysis | ||
| Beginning balance | $ 39,451 | $ 45,125 |
| Adjustment due to changes in estimates | 2,166 | (5,431) |
| Accretion of liability | 3,373 | 4,863 |
| Liabilities settled | (2,712) | (4,104) |
| Foreign Currency | 2,501 | (1,002) |
| Ending balance | $ 44,779 | $ 39,451 |