Derivatives and Fair Value Measurements (Details 1) (USD $) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in other comprehensive income on derivative (effective portion)	$ 218.8	$ (320.8)	$ 326.2	$ 54.0
Gain (loss) reclassified from other comprehensive income into income (effective portion)	93.2	100.7	315.6	289.5
Gain (loss) reclassified from other comprehensive income into income (ineffective portion)	2.2	(1.2)	(2.3)	0.4
Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income on non-designated derivatives	0	0	0	0
Explosives Hedge Contracts Member
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) to be reclassified from comprehensive income to earnings over the next 12 months			(4.0)
Foreign Exchange Contract [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) to be reclassified from comprehensive income to earnings over the next 12 months			287.0
Foreign Exchange Contract [Member] | Operating costs and expenses [Member] | Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in other comprehensive income on derivative (effective portion)	169.2	(269.1)	297.5	33.8
Gain (loss) reclassified from other comprehensive income into income (effective portion)	82.0	92.2	276.6	261.1
Gain (loss) reclassified from other comprehensive income into income (ineffective portion)	0	0	0	0
Foreign Exchange Contract [Member] | Operating costs and expenses [Member] | Cash flow hedges [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income on non-designated derivatives	0	0	0	0
Foreign Exchange Contract [Member] | Depreciation, depletion and amortization [Member] | Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in other comprehensive income on derivative (effective portion)		(0.5)		(0.7)
Gain (loss) reclassified from other comprehensive income into income (effective portion)		0		0
Gain (loss) reclassified from other comprehensive income into income (ineffective portion)		0		0
Foreign Exchange Contract [Member] | Depreciation, depletion and amortization [Member] | Cash flow hedges [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income on non-designated derivatives		0		0
Commodity contracts [Member] | Operating costs and expenses [Member] | Cash flow hedges [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in other comprehensive income on derivative (effective portion)	49.6	(51.2)	28.7	20.9
Gain (loss) reclassified from other comprehensive income into income (effective portion)	11.2	8.5	39.0	28.4
Gain (loss) reclassified from other comprehensive income into income (ineffective portion)	2.2	(1.2)	(2.3)	0.4
Commodity contracts [Member] | Operating costs and expenses [Member] | Cash flow hedges [Member] | Not Designated as Hedging Instrument [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) recognized in income on non-designated derivatives	0	0	0	0
Diesel Fuel Hedge Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Unrealized gains (losses) to be reclassified from comprehensive income to earnings over the next 12 months			$ 30.0