Investments in Affiliates (Details) - USD ($) $ in Millions	3 Months Ended			6 Months Ended
	Jun. 30, 2015	Mar. 31, 2015	Jun. 30, 2014	Jun. 30, 2015	Jun. 30, 2014
Schedule of Equity Method Investments [Line Items]
Impairment of Magnetation investment	$ 0.0		$ 0.0	$ 256.3	$ 0.0
Revenue	76.4		85.3	208.0	157.7
Gross profit	21.4		23.6	28.3	48.1
Net income (loss)	$ 5.8		5.0	$ (18.8)	10.5
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		2.9	$ 3.6	5.1
Other Nonoperating Income (Expense) [Member]
Schedule of Equity Method Investments [Line Items]
Income (Loss) from Equity Method Investments			$ (2.5)	$ (16.3)	$ (3.8)