Derivatives and Fair Value Measurements (Details) (USD $) In Millions, unless otherwise specified			3 Months Ended	12 Months Ended					12 Months Ended					12 Months Ended
	Mar. 31, 2013	Dec. 31, 2012	Mar. 31, 2013 Foreign Currency Forward Contract [Member]	Mar. 31, 2014 Foreign Currency Forward Contract [Member]	Mar. 31, 2013	Mar. 31, 2013 Fair value hedge [Member]	Mar. 31, 2013 Cash flow hedges [Member]	Mar. 31, 2013 Economic hedge [Member]	Mar. 31, 2014 Diesel fuel hedge contracts [Member]	Mar. 31, 2013 Diesel fuel hedge contracts [Member]	Mar. 31, 2013 Diesel fuel hedge contracts [Member] Fair value hedge [Member] gal	Mar. 31, 2013 Diesel fuel hedge contracts [Member] Cash flow hedges [Member] gal	Mar. 31, 2013 Diesel fuel hedge contracts [Member] Economic hedge [Member] gal	Mar. 31, 2014 Explosives Hedge Contracts Member	Mar. 31, 2013 Explosives Hedge Contracts Member	Mar. 31, 2013 Explosives Hedge Contracts Member Fair value hedge [Member] MMbtu	Mar. 31, 2013 Explosives Hedge Contracts Member Cash flow hedges [Member] MMbtu	Mar. 31, 2013 Explosives Hedge Contracts Member Economic hedge [Member] MMbtu
Derivatives, Fair Value [Line Items]
Held-to-maturity Securities	$ 4.8	$ 4.8
Unrealized gains (losses) to be reclassified from comprehensive income to earnings over the next 12 months				205					8					2
Notional Amount of Interest Rate Derivatives	0
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total					4,466.1	0	4,466.1	0
2012					1,510.5
2013					1,688.5
2014					1,097.1
2015					170.0
Total (gallons/MMbtu)											0	194,400,000	0			0	3,100,000	0
2012 (gallons/MMbtu)												76,700,000					1,900,000
2013 (gallons/MMbtu)												73,400,000					1,200,000
2014 (gallons/MMbtu)												44,300,000					0
2015 (gallons/MMbtu)												0					0
Fair Value Asset (Liability)					$ 240.5					$ 6.0					$ (3.0)
Timing differences between the hedge settlement and the purchase transaction			Less than a day and up to a maximum of 30 days