Commitments and Contingencies (Details 2) In Millions, unless otherwise specified	3 Months Ended		9 Months Ended					1 Months Ended	9 Months Ended				3 Months Ended	9 Months Ended
	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2012 USD ($)	Sep. 30, 2011 USD ($)	Sep. 30, 2012 Monto Coal Pty Limited [Member] AUD	Sep. 30, 2012 Gulf Power Company Litigation [Member] USD ($) T	Sep. 30, 2010 Gulf Power Company Litigation [Member] USD ($)	Jun. 30, 2005 Oklahoma Lead Litigation [Member] USD ($)	Sep. 30, 2012 Oklahoma Lead Litigation [Member] USD ($) sites leadmills	Dec. 31, 2011 Oklahoma Lead Litigation [Member] USD ($)	Oct. 23, 2012 Patriot Coal Company [Member] plaintiffs	Jan. 19, 2012 Pending or Threatened Litigation [Member] Gulf Power Company Litigation [Member] USD ($)	Sep. 30, 2012 Macarthur [Member] USD ($)	Sep. 30, 2012 Macarthur [Member] USD ($)
Loss Contingencies [Line Items]
Income (Loss) from Continuing Operations before Income Taxes, Extraordinary Items, Noncontrolling Interest	$ 172.2	$ 330.4	$ 605.9	$ 1,030.1									$ (4.4)	$ 98.7
Loss Contingency [Abstract]
Damages sought for alleged past and future tonnage shortfalls						5,000,000
Litigation Settlement Damages Awarded to Plaintiff		20.5		20.5			0
Litigation Settlement, Prejudgement Interest												6.9
Loss Contingency Accrual, at Carrying Value						0
Ownership Percentage In Subsidiaries					51.00%
Loss Contingency, Damages Sought, Value					1,193.2
Number of lead mills formerly operated by predecessor of subsidiary									2
Percentage of total amount of crude ore mined in Picher, Oklahoma									0.15%
Alleged residential yard remediation costs incurred by the EPA due to potentially responsible parties' activities								125
Number of individual plaintiffs involved in class action lawsuit											8
Number of national priority list sites based on the Superfund Amendments and Reauthorization Act of 1986 at which Gold Fields or the former affiliate, has been named a potentially responsible party (PRP)									5
Number of additional national priority list sites in which claims were asserted									13
Total number of national priority list sites									18
Reduced number of national priority list sites due to completion of work, transfer or regulatory inactivity									10
Undiscounted environmental clean-up liabilities, total									48.7	52.5
Undiscounted environmental clean-up liabilities, current									$ 7.8	$ 11.6