DOCUMENT AND ENTITY INFORMATION (USD $)	12 Months Ended
	Dec. 31, 2011	Mar. 23, 2012
Entity Registrant Name	FIRST BANKS, INC
Entity Central Index Key	0000710507
Current Fiscal Year End Date	--12-31
Entity Filer Category	Non-accelerated Filer
Trading Symbol	fbspra
Entity Common Stock, Shares Outstanding		23,661
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2011
Document Fiscal Period Focus	FY
Document Fiscal Year Focus	2011
Entity Well-Known Seasoned Issuer	No
Entity Voluntary Filers	Yes
Entity Current Reporting Status	Yes
Entity Public Float		$ 0