Derivatives and Fair Value Measurements (Details) In Millions, unless otherwise specified		3 Months Ended
	Mar. 31, 2012 Interest Rate Swap [Member] derivatives	Mar. 31, 2012 Foreign Currency Contracts [Member]	Mar. 31, 2012 GBP to US Hedge Contracts [Member] GBP (£)	Mar. 31, 2012 GBP to US Hedge Contracts [Member] Fair value hedge [Member] GBP (£)	Mar. 31, 2012 GBP to US Hedge Contracts [Member] Cash flow hedges [Member] GBP (£)	Mar. 31, 2012 GBP to US Hedge Contracts [Member] Economic hedge [Member] GBP (£)	Mar. 31, 2012 AUD to USD Hedge Contracts [Member] AUD	Mar. 31, 2012 AUD to USD Hedge Contracts [Member] Fair value hedge [Member] AUD	Mar. 31, 2012 AUD to USD Hedge Contracts [Member] Cash flow hedges [Member] AUD	Mar. 31, 2012 AUD to USD Hedge Contracts [Member] Economic hedge [Member] AUD	Mar. 31, 2012 Diesel fuel hedge contracts [Member] USD ($) gal	Mar. 31, 2012 Diesel fuel hedge contracts [Member] Fair value hedge [Member] gal	Mar. 31, 2012 Diesel fuel hedge contracts [Member] Cash flow hedges [Member] gal	Mar. 31, 2012 Diesel fuel hedge contracts [Member] Economic hedge [Member] gal	Mar. 31, 2012 Explosives Hedge Contracts Member USD ($) MMbtu	Mar. 31, 2012 Explosives Hedge Contracts Member Fair value hedge [Member] MMbtu	Mar. 31, 2012 Explosives Hedge Contracts Member Cash flow hedges [Member] MMbtu	Mar. 31, 2012 Explosives Hedge Contracts Member Economic hedge [Member] MMbtu
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total			£ 6.5	£ 0	£ 6.5	£ 0	4,565.5	0	4,565.5	0
2012			6.5				1,694.9
2013			0				1,651.6
2014			0				1,117.5
2015			0				101.5
2016			0				0
2017 and thereafter			0				0
Total (gallons/MMbtu)											190,000,000	0	190,000,000	0	6,600,000	0	6,600,000	0
2012 (gallons/MMbtu)											72,300,000				2,800,000
2013 (gallons/MMbtu)											73,700,000				2,600,000
2014 (gallons/MMbtu)											41,000,000				1,200,000
2015 (gallons/MMbtu)											3,000,000				0
2016 (gallons/MMbtu)											0				0
2017 and thereafter (gallons/MMbtu)											0				0
Fair Value Asset (Liability)			£ 0				517.9				$ 81.9				$ (12.7)
Timing differences between the hedge settlement and the purchase transaction		Less than a day and up to a maximum of 30 days
Number of Interest Rate Derivatives Held	0