BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES - Equity Method Investments (Details) - USD ($) $ in Millions |
Jun. 30, 2020 |
Mar. 13, 2020 |
|---|---|---|
| Combined Metals of Chicago, LLC [Member] | Ìý | Ìý |
| Schedule of Equity Method Investments [Line Items] | Ìý | Ìý |
| Equity Method Investment, Ownership Percentage | 40.00% | Ìý |
| Hibbing Taconite Company [Member] | Ìý | Ìý |
| Schedule of Equity Method Investments [Line Items] | Ìý | Ìý |
| Equity Method Investment, Ownership Percentage | 23.00% | Ìý |
| Spartan Steel Coating, LLC [Member] | Ìý | Ìý |
| Schedule of Equity Method Investments [Line Items] | Ìý | Ìý |
| Equity Method Investment, Difference Between Carrying Amount and Underlying Equity | Ìý | $ 32.5 |
| Equity Method Investment, Ownership Percentage | 48.00% | Ìý |
| X | ||||||||||
- Definition Difference between amount at which an investment accounted for under the equity method of accounting is carried (reported) on the balance sheet and amount of underlying equity in net assets the reporting Entity has in the investee. Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
|
| X | ||||||||||
- Definition The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting. 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
|
| X | ||||||||||
- Details
|
| X | ||||||||||
- Details
|