Derivatives and Fair Value Measurements (Details 2) (USD $) In Millions, unless otherwise specified	Mar. 31, 2014	Dec. 31, 2013
Foreign currency cash flow hedge contract [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	$ (238.0)
Explosives Hedge Contracts Member
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	(0.5)
Diesel Fuel Hedge Contracts [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	(0.5)
Fair Value, Measurements, Recurring [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Investments in debt and equity securities (available-for-sale)	65.5	67.0
Total net financial assets (liabilities)	(173.5)	(401.2)
Fair Value, Measurements, Recurring [Member] | Foreign currency cash flow hedge contract [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	(238.0)	(473.3)
Fair Value, Measurements, Recurring [Member] | Commodity swaps and options [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	(1.0)	5.1
Fair Value, Measurements, Recurring [Member] | Level 1[Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Investments in debt and equity securities (available-for-sale)	25.7	28.8
Total net financial assets (liabilities)	25.7	28.8
Fair Value, Measurements, Recurring [Member] | Level 1[Member] | Foreign currency cash flow hedge contract [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	0	0
Fair Value, Measurements, Recurring [Member] | Level 1[Member] | Commodity swaps and options [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	0	0
Fair Value, Measurements, Recurring [Member] | Level 2 [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Investments in debt and equity securities (available-for-sale)	39.8	38.2
Total net financial assets (liabilities)	(199.2)	(430.0)
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Foreign currency cash flow hedge contract [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	(238.0)	(473.3)
Fair Value, Measurements, Recurring [Member] | Level 2 [Member] | Commodity swaps and options [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	(1.0)	5.1
Fair Value, Measurements, Recurring [Member] | Level 3 [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Investments in debt and equity securities (available-for-sale)	0	0
Total net financial assets (liabilities)	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Foreign currency cash flow hedge contract [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	0	0
Fair Value, Measurements, Recurring [Member] | Level 3 [Member] | Commodity swaps and options [Member]
Fair value of financial asset (liability) positions measured on a recurring basis
Derivative assets (liabilities), at fair value, net	$ 0	$ 0