Investments in Affiliates (Details) - USD ($) $ in Millions	3 Months Ended			9 Months Ended
	Sep. 30, 2015	Mar. 31, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014
Schedule of Equity Method Investments [Line Items]
Impairment of Magnetation investment	$ 0.0		$ 0.0	$ 256.3	$ 0.0
Revenue	76.1		87.4	284.1	245.1
Gross profit	20.7		25.3	49.0	73.3
Net income (loss)	$ 5.1		7.3	$ (13.7)	17.7
Iron Ore [Member]
Schedule of Equity Method Investments [Line Items]
Spot Commodities, Price Increase (Decrease), Percentage		(20.00%)
Magnetation LLC [Member]
Schedule of Equity Method Investments [Line Items]
Equity Method Investment, Ownership Percentage	49.90%			49.90%
Impairment of Magnetation investment		$ 256.3
Cost of Sales [Member]
Schedule of Equity Method Investments [Line Items]
Income (Loss) from Equity Method Investments	$ 1.8		3.4	$ 5.4	8.5
Other Nonoperating Income (Expense) [Member]
Schedule of Equity Method Investments [Line Items]
Income (Loss) from Equity Method Investments			$ (2.2)	$ (16.3)	$ (6.0)