Retirement Benefits - Narrative (Details) (USD $) In Millions, except Share data, unless otherwise specified	12 Months Ended						12 Months Ended			12 Months Ended			12 Months Ended					12 Months Ended					12 Months Ended			12 Months Ended		12 Months Ended
	Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Dec. 31, 2011 US Plans [Member]	Dec. 31, 2010 US Plans [Member]	Dec. 31, 2009 US Plans [Member]	Dec. 31, 2011 Non-US Plans [Member]	Dec. 31, 2010 Non-US Plans [Member]	Dec. 31, 2009 Non-US Plans [Member]	Dec. 31, 2011 UMWA plans [Member]	Dec. 31, 2010 UMWA plans [Member]	Dec. 31, 2009 UMWA plans [Member]	Dec. 31, 2011 Black lung and other plans - postretirement medical [Member]	Dec. 31, 2010 Black lung and other plans - postretirement medical [Member]	Dec. 31, 2009 Black lung and other plans - postretirement medical [Member]	Dec. 31, 2010 Black lung and other plans - postretirement medical [Member] Before Restatement Date [Member]	Dec. 31, 2010 Black lung and other plans - postretirement medical [Member] After Restatement Date [Member]	Dec. 31, 2011 Pension plan [Member]	Dec. 31, 2010 Pension plan [Member]	Dec. 31, 2008 Pension plan [Member]	Dec. 31, 2009 Pension plan [Member] Before Restatement Date [Member]	Dec. 31, 2009 Pension plan [Member] After Restatement Date [Member]	Dec. 31, 2011 Retirement benefits other than pension [Member]	Dec. 31, 2010 Retirement benefits other than pension [Member]	Dec. 31, 2009 Retirement benefits other than pension [Member]	Dec. 31, 2009 Primary U.S. retirement plan [Member]	Dec. 31, 2011 Nonqualified U.S. pension plan [Member]	Dec. 31, 2011 U.S. 401 (K) Expense [Member]	Dec. 31, 2010 U.S. 401 (K) Expense [Member]	Dec. 31, 2009 U.S. 401 (K) Expense [Member]	Dec. 31, 2011 Other Defined Contribution Plans Expense [Member]	Dec. 31, 2010 Other Defined Contribution Plans Expense [Member]	Dec. 31, 2009 Other Defined Contribution Plans Expense [Member]
Amounts in AOCI to be recognized in retirement cost in next fiscal year [Abstract]
Net Gains Losses to be recognized in retirement cost next fiscal year																		$ 44.6					$ 22.4
Net Prior Service Cost Credit to be recognized in retirement cost next fiscal year																		1.4					2.0
Accumulated benefit obligation				990.7	890.1		278.8	259.8
Estimated contributions				31.5			26.9																				13.2
Excise Tax Rate										4.20%
UMWA obligation increase due to "Cadillac" plan excise tax	253.6	67.8	(68.2)	(133.1)	(60.5)		(20.0)	(4.1)		97.6	4.5		2.9	(1.3)				(153.1)	(64.6)				100.5	3.2							21.3
Retirement Benefit Plan Remeasurements [Abstract]
Remeasurement date														March 31 2010												July 01, 2009
Voluntary contribution																										150
Cash portion of contribution																										92.4
Newly issued shares of common stock for contribution																										2,260,738
Common stock value per share for stock contribution																										$ 25.48
Aggregate value of shares of common stock contribution			57.6																							57.6
Remeasurement discount rate	4.60%	5.30%	5.90%				5.40%	5.80%	6.20%	4.40%	5.30%	5.90%	4.20%	4.80%	5.40%						6.20%	6.80%	4.40%	5.20%	5.90%
2010 Healthcare reform black lung obligation increase	0	19.3	0							0	0		0	19.3									0	19.3
Black lung obligation				990.7	890.1	810.5	306.9	289.6	223.4	529.6	474.3	465.5	60.9	62.2	47.1	42.3	61.6	1,297.6	1,179.7	1,033.9			590.5	536.5	512.6
Black lung health care cost trend rate										7.00%	7.00%			5.00%
Black lung health care cost ultimate rate										5.00%	5.00%
UMWA Medical Plans with Prescription Drug Benefits [Abstract]
Estimated reduction in per capita claim costs for participants over 65 years old	8.60%
Effect of Subsidy on Net Periodic Postretirement Benefit Cost	4.5	4.5	4.3
Reduction in Accumulated Postretirement Benefit Obligation for Subsidy	60.2	50.2
Other Benefit Plans [Abstract]
Multiemployer Pension Expense		2.3	2.1
Matching defined contribution expense	$ 20.8	$ 20.3	$ 16.8																									$ 16.9	$ 16.3	$ 13.4	$ 3.9	$ 4.0	$ 3.4