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BASIS OF PRESENTATION AND SIGNIFICANT ACCOUNTING POLICIES (Tables) | 9 Months Ended
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Sep. 30, 2017
Organization, Consolidation and Presentation of Financial Statements [Abstract] |
Schedule Of Subsidiaries | The unaudited condensed consolidated financial statements include our accounts and the accounts of our wholly-owned subsidiaries, including the following operations as of September 30, 2017:
Name |  | Location |  | Ownership Interest |  | Operation |  | Status of Operations
Northshore |  | Minnesota |  | 100.0% |  | Iron Ore |  | Active
United Taconite |  | Minnesota |  | 100.0% |  | Iron Ore |  | Active
Tilden 1 |  | Michigan |  | 100.0% |  | Iron Ore |  | Active
Empire 1 |  | Michigan |  | 100.0% |  | Iron Ore |  | Indefinitely Idled
Koolyanobbing |  | Western Australia |  | 100.0% |  | Iron Ore |  | Active
1 During the third quarter of 2017, our ownership interest in Tilden and Empire changed. Refer to the Noncontrolling Interests section below for additional information.
Foreign Currency Transaction [Table Text Block] | The following represents the transaction gains and losses resulting from remeasurement for the three and nine months ended September 30, 2017 and 2016:
|  | (In Millions)
|  | Three Months Ended September 30, |  | Nine Months Ended September 30,
|  | 2017 |  | 2016 |  | 2017 |  | 2016
Remeasurement of short-term intercompany loans |  | $ | 0.1 |  |  | $ | 0.2 |  |  | $ | 16.7 |  |  | $ | 0.5 |
Remeasurement of cash and cash equivalents |  | (1.1 | ) |  | (1.1 | ) |  | (2.8 | ) |  | 0.3 |
Other remeasurement |  | (1.4 | ) |  | 0.6 |  |  | (2.7 | ) |  | (2.0 | )
Net impact of transaction gains (losses) resulting from remeasurement |  | $ | (2.4 | ) |  | $ | (0.3 | ) |  | $ | 11.2 |  |  | $ | (1.2 | )
Adoption of New Standard [Table Text Block] | The following represents the estimated impact from the adoption of ASU No. 2017-07 for the nine months ended September 30, 2017:
|  | ($ in Millions)
|  | Nine Months Ended September 30, 2017
|  |  |  | Estimate
Financial Statement Line Impacted |  | As Reported |  | Adoption of ASU No. 2017-07 |  | As Adjusted
Cost of goods sold and operating expenses |  | $ | (1,328.3 | ) |  | $ | 1.3 |  |  | $ | (1,327.0 | )
Selling, general and administrative expenses |  | $ | (77.8 | ) |  | $ | (5.8 | ) |  | $ | (83.6 | )
Miscellaneous - net |  | $ | 3.0 |  |  | $ | (1.2 | ) |  | $ | 1.8 |
Operating income |  | $ | 326.2 |  |  | $ | (5.7 | ) |  | $ | 320.5 |
Other non-operating income |  | $ | 2.3 |  |  | $ | 5.7 |  |  | $ | 8.0 |
Net Income (Loss) |  | $ | 53.2 |  |  | $ | — |  |  | $ | 53.2 |

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