Commitments and Contingencies (Details 2) In Millions, unless otherwise specified							12 Months Ended		12 Months Ended
	Dec. 31, 2012 USD ($)	Dec. 31, 2011 USD ($)	Sep. 30, 2011 USD ($)	Dec. 31, 2012 Gulf Power Company Litigation [Member] USD ($) T	Jan. 19, 2012 Gulf Power Company Litigation [Member] USD ($)	Sep. 30, 2010 Gulf Power Company Litigation [Member] USD ($)	Dec. 31, 2012 Oklahoma Lead Litigation [Member] USD ($) sites	Dec. 31, 2011 Oklahoma Lead Litigation [Member] USD ($)	Dec. 31, 2012 Monto Coal Pty Limited [Member] AUD	Oct. 23, 2012 Patriot Coal Company [Member] plaintiffs
Loss Contingency [Abstract]
Alleged shortage of past and future coal shipments under a coal supply agreement, tons				5,000,000
Litigation Settlement Damages Awarded to Plaintiff			$ 20.5			$ 0
Litigation Settlement, Prejudgement Interest					6.9
Loss Contingency Accrual, at Carrying Value				0
Ownership Percentage In Subsidiaries									51.00%
Minimum actual damages sought by plaintiff									1,193.2
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							46.7	52.5
Accrued environmental	$ 10.6	$ 11.6					$ 10.6	$ 11.6