ENVIRONMENTAL AND MINE CLOSURE OBLIGATIONS (Summary Of Mine Closure Obligations) (Details) - USD ($) $ in Millions |
Mar. 31, 2019 |
Dec. 31, 2018 |
Dec. 31, 2017 |
|---|---|---|---|
| Loss Contingencies [Line Items] | |||
| Environmental | $ 2.4 | $ 2.5 | |
| Asset Retirement Obligation | 174.9 | 172.4 | $ 168.4 |
| Environmental Loss Contingency And Mine Reclamation And Closing Liability Current And Noncurrent | 177.3 | 174.9 | |
| Environmental Loss Contingency And Mine Reclamation And Closing Liability Current | 2.9 | 2.9 | |
| Environmental Loss Contingency And Mine Reclamation And Closing Liability Noncurrent | 174.4 | 172.0 | |
| Mining and Pelletizing [Member] | |||
| Loss Contingencies [Line Items] | |||
| Asset Retirement Obligation | $ 174.9 | $ 172.4 |
| X | ||||||||||
- Definition Environmental Loss Contingency And Mine Reclamation And Closing Liability Current No definition available.
|
| X | ||||||||||
- Definition Environmental Loss Contingency And Mine Reclamation And Closing Liability Current And Noncurrent No definition available.
|
| X | ||||||||||
- Definition Amount of environmental loss contingencies, such as presence of hazardous waste, relevant information from reports issued by regulators, and estimated costs to achieve compliance with regulatory requirements. As well as, the amount of a reclamation and mine closing liability that is associated with a legal obligation for the closure and reclamation of a mine including the removal of buildings, equipment, machinery and other physical remnants of mining, closure of tailings impoundments, leach pads and other mine features, and contouring, covering and revegetation of waste rock piles and other disturbed areas. No definition available.
|
| X | ||||||||||
- Definition Total costs accrued as of the balance sheet date for environmental loss contingencies. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition The carrying amount of a liability for an asset retirement obligation. An asset retirement obligation is a legal obligation associated with the disposal or retirement of a tangible long-lived asset that results from the acquisition, construction or development, or the normal operations of a long-lived asset, except for certain obligations of lessees. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. No definition available.
|
| X | ||||||||||
- Details
|