Derivatives and Fair Value Measurements (Details) In Millions, unless otherwise specified	12 Months Ended								12 Months Ended					12 Months Ended
	Dec. 31, 2013	Dec. 31, 2014 Foreign currency forward contract [Member] USD ($)	Dec. 31, 2013 Foreign currency forward contract [Member] USD ($)	Dec. 31, 2013 Foreign currency forward contract [Member] AUD	Dec. 31, 2013 Foreign currency forward contract [Member] Fair value hedge [Member] AUD	Dec. 31, 2013 Foreign currency forward contract [Member] Cash flow hedges [Member] AUD	Dec. 31, 2012 Foreign currency forward contract [Member] Cash flow hedges [Member] AUD	Dec. 31, 2013 Foreign currency forward contract [Member] Economic hedge [Member] AUD	Dec. 31, 2014 Diesel fuel hedge contracts [Member] USD ($)	Dec. 31, 2013 Diesel fuel hedge contracts [Member] USD ($) gal	Dec. 31, 2013 Diesel fuel hedge contracts [Member] Fair value hedge [Member] gal	Dec. 31, 2013 Diesel fuel hedge contracts [Member] Cash flow hedges [Member] gal	Dec. 31, 2013 Diesel fuel hedge contracts [Member] Economic hedge [Member] gal	Dec. 31, 2014 Explosives hedge contracts [Member] USD ($)	Dec. 31, 2013 Explosives hedge contracts [Member] USD ($) MMbtu	Dec. 31, 2013 Explosives hedge contracts [Member] Fair value hedge [Member] MMbtu	Dec. 31, 2013 Explosives hedge contracts [Member] Cash flow hedges [Member] MMbtu	Dec. 31, 2013 Explosives hedge contracts [Member] Economic hedge [Member] MMbtu
Derivatives, Fair Value [Line Items]
Gains (losses) to be reclassified from accumulated other comprehensive income		$ (75)							$ 6					$ (1)
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total (A$ millions)				5,203.6	0	5,203.6	1,900.0	0
2014 (A$ millions)				2,074.5
2015 (A$ millions)				1,645.1
2016 (A$ millions)				997.0
2017 (A$ millions)				487.0
Total (gallons/MMbtu)										203,700,000	0	203,700,000	0		1,200,000	0	1,200,000	0
2014 (gallons/MMbtu)										101,000,000					1,200,000
2015 (gallons/MMbtu)										68,600,000					0
2016 (gallons/MMbtu)										34,100,000					0
2017 (gallons/MMbtu)										0					0
Fair value asset (liability)			$ (473.3)							$ 6.4					$ (1.3)
Timing differences between the hedge settlement and the purchase transaction	Less than a day and up to a maximum of 30 days