Document and Entity Information Document	9 Months Ended
Sep. 30, 2011	Oct. 28, 2011
Document and Entity Information [Abstract]
Entity Registrant Name	PEABODY ENERGY CORP
Entity Central Index Key	0001064728
Document Type	10-Q
Document Period End Date	Sep. 30, 2011
Amendment Flag	false
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	Q3
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		270,874,294

Document And Entity Information.

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