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.

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 323
-SubTopic 10
-Section 50
-Paragraph 3
-Subparagraph (a)(3)
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This item represents an other than temporary decline in value that has been recognized against an investment accounted for under the equity method of accounting. The excess of the carrying amount over the fair value of the investment represents the amount of the write down which is or was reflected in earnings. The written down value is a new cost basis with the adjusted value of the investment becoming its new carrying value subject to the equity accounting method. Evidence of a loss in value might include, but would not necessarily be limited to, absence of an ability to recover the carrying amount of the investment or inability of the investee to sustain an earnings capacity which would justify the carrying amount of the investment.

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- Definition

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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-Name Accounting Standards Codification
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Gain (loss) related to the termination of a contract between the parties. The termination may be due to many causes including early termination of a lease by a lessee, a breach of contract by one party, or a failure to perform.

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This item represents the entity's proportionate share for the period of the net income (loss) of its investee (such as unconsolidated subsidiaries and joint ventures) to which the equity method of accounting is applied. This item includes income or expense related to stock-based compensation based on the investor's grant of stock to employees of an equity method investee.

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-Subparagraph (SX 210.5-03(12))
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Losses recognized in the current period on contracts which are expected to generate losses, which are probable and can be reasonably estimated, in a future period.

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The amount of cash paid for the settlement of litigation or for other legal issues during the period.

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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.

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No definition available.

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Investments in Affiliates (Details) - USD ($) $ in Millions		3 Months Ended			12 Months Ended
Investments in Affiliates (Details) - USD ($) $ in Millions	Oct. 07, 2016	Dec. 31, 2017	Dec. 31, 2016	Mar. 31, 2015	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Other than Temporary Impairment					$ 0.0	$ 0.0	$ 256.3
Gain on termination of pellet agreement and related transportation costs					$ 19.3	(69.5)	0.0
Combined Metals of Chicago, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage (in hundredths)		40.00%			40.00%
Delaco Processing, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage (in hundredths)		49.00%			49.00%
Rockport Roll Shop LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage (in hundredths)		50.00%			50.00%
Spartan Steel Coating, LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage (in hundredths)		48.00%			48.00%
Difference between carrying amount and underlying equity		$ 10.8			$ 10.8
Magnetation LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity method investment, ownership percentage (in hundredths)				49.90%
Equity Method Investment, Other than Temporary Impairment				$ 256.3
Other Income (Expense) [Member] \| Magnetation LLC [Member]
Schedule of Equity Method Investments [Line Items]
Share of income (loss) from equity method investments							(16.3)
Cost of Products Sold [Member]
Schedule of Equity Method Investments [Line Items]
Share of income (loss) from equity method investments					7.0	12.3	$ 6.7
Global Settlement Agreement [Member]
Schedule of Equity Method Investments [Line Items]
Payments for Legal Settlements	$ 36.6
Iron Ore Pellets Agreements [Member]
Schedule of Equity Method Investments [Line Items]
Loss on Contracts			$ 32.9
Gain on termination of pellet agreement and related transportation costs		$ 19.3	$ (69.5)		$ 19.3	$ (69.5)