Derivatives and Fair Value Measurements (Details) (USD $) In Millions	Jun. 30, 2011
A$:US$ hedge contracts [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	$ 3,902.7
2011	755.6
2012	1,485.0
2013	1,083.6
2014	578.5
2015	0
2016 and thereafter	0
Fair Value Asset (Liability)	773.6
A$:US$ hedge contracts [Member] | Fair value hedge [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	0
A$:US$ hedge contracts [Member] | Cash flow hedges [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	3,902.7
A$:US$ hedge contracts [Member] | Economic hedge [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	0
Diesel fuel hedge contracts [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	187.0
2011	43.8
2012	78.1
2013	49.8
2014	15.3
2015	0
2016 and thereafter	0
Fair Value Asset (Liability)	95.3
Diesel fuel hedge contracts [Member] | Fair value hedge [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	0
Diesel fuel hedge contracts [Member] | Cash flow hedges [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	187.0
Diesel fuel hedge contracts [Member] | Economic hedge [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	0
U.S. explosives hedge contracts [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	7.9
2011	2.0
2012	3.5
2013	2.1
2014	0.3
2015	0
2016 and thereafter	0
Fair Value Asset (Liability)	(1.3)
U.S. explosives hedge contracts [Member] | Fair value hedge [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	0
U.S. explosives hedge contracts [Member] | Cash flow hedges [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	7.9
U.S. explosives hedge contracts [Member] | Economic hedge [Member]
Company's foreign currency and commodity positions by Year of Maturity and Account Classification
Total	$ 0