Derivatives And Other Financial Instruments (Fair Value Of Outstanding Derivative Contracts Recorded As Assets) (Details) (USD $) In Millions	Sep. 30, 2011		Dec. 31, 2010
Fair value asset derivatives	$ 94		$ 147
Prepaid Expenses And Other Current Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Fair value asset derivatives	9		48
Prepaid Expenses And Other Current Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Foreign Exchange Contracts [Member]
Fair value asset derivatives	1		2
Prepaid Expenses And Other Current Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Interest Rate Contracts [Member]
Fair value asset derivatives	8		19
Prepaid Expenses And Other Current Assets [Member] | Margins Held [Member] | Aluminum Contracts [Member]
Fair value asset derivatives			4
Prepaid Expenses And Other Current Assets [Member] | Margins Held [Member] | Interest Rate Contracts [Member]
Fair value asset derivatives	5		13
Prepaid Expenses And Other Current Assets [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Fair value asset derivatives	1	[1]	3	[1]
Other Noncurrent Assets [Member]
Fair value asset derivatives	20		19
Other Noncurrent Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Fair value asset derivatives	9		22
Other Noncurrent Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Energy Contract [Member]
Fair value asset derivatives	40		9
Other Noncurrent Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Interest Rate Contracts [Member]
Fair value asset derivatives	41		62
Other Noncurrent Assets [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Fair value asset derivatives	5	[1]
Other Noncurrent Assets [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Foreign Exchange Contracts [Member]
Fair value asset derivatives			1	[1]
Other Noncurrent Assets [Member] | Interest Rate Contracts [Member]
Fair value asset derivatives	15		2
Derivatives Designated As Hedging Instruments [Member]
Fair value asset derivatives	108		162
Derivatives Not Designated As Hedging Instruments [Member]
Fair value asset derivatives	$ 6	[1]	$ 4	[1]

[1] See the "Other" section within Note P for additional information on Alcoa's purpose for entering into derivatives not designated as hedging instruments and its overall risk management strategies.