Document And Entity Information (USD $)	12 Months Ended
	Dec. 31, 2011	Feb. 10, 2012	Jun. 30, 2011
Document And Entity Information [Abstract]
Document Type	10-K
Amendment Flag	false
Document Period End Date	Dec. 31, 2011
Document Fiscal Year Focus	2011
Document Fiscal Period Focus	FY
Trading Symbol	aa
Entity Registrant Name	ALCOA INC
Entity Central Index Key	0000004281
Current Fiscal Year End Date	--12-31
Entity Filer Category	Large Accelerated Filer
Entity Common Stock, Shares Outstanding		1,066,107,670
Entity Public Float			$ 17,000,000,000
Entity Voluntary Filers	No
Entity Current Reporting Status	Yes
Entity Well-known Seasoned Issuer	Yes