Derivatives and Fair Value Measurements (Details) In Millions, unless otherwise specified	6 Months Ended															12 Months Ended
	Jun. 30, 2014	Jun. 30, 2014 Interest Rate Swap [Member] USD ($)	Jun. 30, 2014 Foreign Currency Forward Contract [Member] USD ($)	Jun. 30, 2014 Foreign Currency Forward Contract [Member] AUD	Jun. 30, 2014 Foreign Currency Forward Contract [Member] Fair value hedge [Member] AUD	Jun. 30, 2014 Foreign Currency Forward Contract [Member] Cash flow hedges [Member] AUD	Jun. 30, 2014 Foreign Currency Forward Contract [Member] Economic hedge [Member] AUD	Jun. 30, 2014 Diesel fuel hedge contracts [Member] USD ($) gal	Jun. 30, 2014 Diesel fuel hedge contracts [Member] Fair value hedge [Member] gal	Jun. 30, 2014 Diesel fuel hedge contracts [Member] Cash flow hedges [Member] gal	Jun. 30, 2014 Diesel fuel hedge contracts [Member] Economic hedge [Member] gal	Jun. 30, 2014 Explosives Hedge Contracts Member USD ($) MMbtu	Jun. 30, 2014 Explosives Hedge Contracts Member Fair value hedge [Member] MMbtu	Jun. 30, 2014 Explosives Hedge Contracts Member Cash flow hedges [Member] MMbtu	Jun. 30, 2014 Explosives Hedge Contracts Member Economic hedge [Member] MMbtu	Jun. 30, 2015 Scenario, Forecast [Member] Foreign Currency Forward Contract [Member] USD ($)	Jun. 30, 2015 Scenario, Forecast [Member] Diesel fuel hedge contracts [Member] USD ($)	Jun. 30, 2015 Scenario, Forecast [Member] Explosives Hedge Contracts Member USD ($)
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total (A$ millions)		$ 0		4,082.1	0	4,082.1	0
2014 (A$ millions)				935.0
2015 (A$ millions)				1,645.1
2016 (A$ millions)				997.0
2017 (A$ millions)				505.0
Total (gallons/MMbtu)								208,500,000	0	208,500,000	0	300,000	0	300,000	0
2014 (gallons/MMbtu)								52,200,000				300,000
2015 (gallons/MMbtu)								85,500,000				0
2016 (gallons/MMbtu)								53,300,000				0
2017 (gallons/MMbtu)								17,500,000				0
Fair Value Net Asset (Liability)			(109.6)					16.0				(0.2)
Gains (losses) to be reclassified from accumulated other comprehensive (loss) income to earnings over the next 12 months																$ 15.0	$ 9.0	$ (0.2)
Timing differences between the hedge settlement and the purchase transaction	Less than a day and up to a maximum of 30 days