Preferred And Common Stock (Schedule Of Unrecognized Compensation Expense) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011
Preferred And Common Stock [Abstract]
2012	$ 41
2013	22
2014	2
Total	$ 65

Share Based Compensation, Unrecognized Compensation Expense Expected To Be Recognized In Year Three

No definition available.

Name:	aa_ShareBasedCompensationUnrecognizedCompensationExpenseExpectedToBeRecognizedInYearThree
Namespace Prefix:	aa_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration