Derivatives And Other Financial Instruments (Schedule Of Fair Values Of Outstanding Derivative Contracts Recorded As Assets) (Details) (USD $) In Millions, unless otherwise specified	Dec. 31, 2011		Dec. 31, 2010
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	$ 94		$ 147
Derivatives Designated As Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	109		162
Derivatives Not Designated As Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	7		4
Prepaid Expenses And Other Current Assets [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	7		4
Prepaid Expenses And Other Current Assets [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	8		13
Prepaid Expenses And Other Current Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	56		48
Prepaid Expenses And Other Current Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives			2
Prepaid Expenses And Other Current Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	8		19
Prepaid Expenses And Other Current Assets [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	1	[1]	3	[1]
Other Noncurrent Assets [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	22		19
Other Noncurrent Assets [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	7		2
Other Noncurrent Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	6		22
Other Noncurrent Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	2		9
Other Noncurrent Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	37		62
Other Noncurrent Assets [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	5	[1]
Other Noncurrent Assets [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Foreign Exchange Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	$ 1		$ 1

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