Derivatives and Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	Sep. 30, 2014	Dec. 31, 2013
Gross amounts of recognized assets/liabilities [Member]
Derivative [Line Items]
Derivative assets, current	$ 0.1	$ 8.7
Derivative assets, noncurrent	0.1	3.0
Derivative liabilities, current	193.6	215.8
Derivative liabilities, noncurrent	150.3	264.1
Gross amounts of recognized assets/liabilities [Member] | Commodity swap contracts [Member]
Derivative [Line Items]
Derivative assets, current		8.7
Derivative assets, noncurrent	0.1	2.8
Derivative liabilities, current	19.9	3.9
Derivative liabilities, noncurrent	8.9	2.5
Gross amounts of recognized assets/liabilities [Member] | Foreign currency forward contract [Member]
Derivative [Line Items]
Derivative assets, current	0.1	0
Derivative assets, noncurrent		0.2
Derivative liabilities, current	173.7	211.9
Derivative liabilities, noncurrent	141.4	261.6
Gross amounts offset in the condensed consolidated balance sheet [Member]
Derivative [Line Items]
Derivative assets, current	(0.1)	(2.3)
Derivative assets, noncurrent	(0.1)	(1.1)
Derivative liabilities, current	0	(1.9)
Derivative liabilities, noncurrent	(0.2)	(1.5)
Gross amounts offset in the condensed consolidated balance sheet [Member] | Commodity swap contracts [Member]
Derivative [Line Items]
Derivative assets, current		(2.3)
Derivative assets, noncurrent	(0.1)	(0.9)
Derivative liabilities, current	0	(1.9)
Derivative liabilities, noncurrent	(0.1)	(1.3)
Gross amounts offset in the condensed consolidated balance sheet [Member] | Foreign currency forward contract [Member]
Derivative [Line Items]
Derivative assets, current	(0.1)	0
Derivative assets, noncurrent		(0.2)
Derivative liabilities, current	0	0
Derivative liabilities, noncurrent	(0.1)	(0.2)
Net amounts presented in the condensed consolidated balance sheet [Member]
Derivative [Line Items]
Derivative assets, current	0	6.4
Derivative assets, noncurrent	0	1.9
Derivative liabilities, current	193.6	213.9
Derivative liabilities, noncurrent	150.1	262.6
Net amounts presented in the condensed consolidated balance sheet [Member] | Commodity swap contracts [Member]
Derivative [Line Items]
Derivative assets, current		6.4
Derivative assets, noncurrent	0	1.9
Derivative liabilities, current	19.9	2.0
Derivative liabilities, noncurrent	8.8	1.2
Net amounts presented in the condensed consolidated balance sheet [Member] | Foreign currency forward contract [Member]
Derivative [Line Items]
Derivative assets, current	0	0
Derivative assets, noncurrent		0
Derivative liabilities, current	173.7	211.9
Derivative liabilities, noncurrent	141.3	261.4
Derivatives not offset in the condensed consolidated balance sheet [Member]
Derivative [Line Items]
Derivative assets, current		(5.0)	[1]
Derivative assets, noncurrent		(1.3)	[1]
Derivative liabilities, current		(5.4)	[1]
Derivative liabilities, noncurrent		(0.9)	[1]
Net amount of derivatives not offset [Member]
Derivative [Line Items]
Derivative assets, current		1.4
Derivative assets, noncurrent		0.6
Derivative liabilities, current		208.5
Derivative liabilities, noncurrent		$ 261.7

[1] Adjustments relate to the further netting of derivative contracts with a common counterparty across the Company's foreign currency, diesel fuel and explosives hedging strategy derivative contract portfolios that would be contractually enforceable in the event of default. Such adjustments were not applicable as of September 30, 2014 due to the consistent net liability position with common counterparties across the Company's foreign currency and diesel fuel hedging strategy derivative contract portfolios as of that date.