ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Narrative) (Details) $ in Millions |
12 Months Ended | |
|---|---|---|
|
Dec. 31, 2016
USD ($)
T
|
Sep. 30, 2017
USD ($)
|
|
| Accrual for Environmental Loss Contingencies, Period Increase (Decrease) | $ 9.2 | |
| Reserve increase (decrease), tons | T | 115,000,000 | |
| Selenium [Domain] | ||
| Accrual for Environmental Loss Contingencies, Period Increase (Decrease) | $ 29.6 | |
| Eastern Canadian Iron Ore [Member] | Owned Or Operating Facilities [Member] | ||
| Mine Reclamation and Closing Liability, current and noncurrent | $ 206.8 | $ 216.2 |
| X | ||||||||||
- Definition Mine Reclamation and Closing Liability, current and noncurrent No definition available.
|
| X | ||||||||||
- Definition Reserve increase (decrease), tons No definition available.
|
| X | ||||||||||
- Definition Increase (decrease) in the accrual for environmental loss contingencies during the reporting period. Reference 1: http://www.xbrl.org/2003/role/presentationRef
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|