BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Schedule Of Subsidiaries) (Details) |
3 Months Ended |
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Mar. 31, 2019 | |
| Northshore | Ìý |
| Related Party Transaction [Line Items] | Ìý |
| Entity Address, State or Province | Minnesota |
| United Taconite | Ìý |
| Related Party Transaction [Line Items] | Ìý |
| Entity Address, State or Province | Minnesota |
| Tilden | Ìý |
| Related Party Transaction [Line Items] | Ìý |
| Entity Address, State or Province | Michigan |
| Empire | Ìý |
| Related Party Transaction [Line Items] | Ìý |
| Entity Address, State or Province | Michigan |
| Metallics [Member] | Ìý |
| Related Party Transaction [Line Items] | Ìý |
| Entity Address, State or Province | Ohio |
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- 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.
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