Document and Entity Information	9 Months Ended
	Sep. 30, 2012	Nov. 08, 2012
Document Information [Line Items]
Document Type	10-Q
Amendment Flag	false
Document Period End Date	Sep. 30, 2012
Document Fiscal Year Focus	2012
Document Fiscal Period Focus	Q3
Trading Symbol	BTFG
Entity Registrant Name	BANCTRUST FINANCIAL GROUP INC
Entity Central Index Key	0000783739
Current Fiscal Year End Date	--12-31
Entity Filer Category	Smaller Reporting Company
Entity Common Stock, Shares Outstanding		17,966,308