Derivatives And Other Financial Instruments (Schedule Of Fair Values Of Outstanding Derivative Contracts Recorded As Liabilities) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	$ 781		$ 737
Derivatives Designated As Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	700		653
Derivatives Not Designated As Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	81	[1]	85	[1]
Level 1 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	22		64
Level 1 [Member] | Other Current Liabilities [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	13		47
Level 1 [Member] | Other Current Liabilities [Member] | Derivatives Designated As Hedging Instruments [Member] | Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	1
Level 1 [Member] | Other Current Liabilities [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	6	[1]	12	[1]
Level 1 [Member] | Other Current Liabilities [Member] | Margin Posted [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives			1	[2]
Level 1 [Member] | Other Noncurrent Liabilities And Deferred Credits [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	1		4
Level 1 [Member] | Other Noncurrent Liabilities And Deferred Credits [Member] | Derivatives Designated As Hedging Instruments [Member] | Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	1
Level 1 [Member] | Other Noncurrent Liabilities And Deferred Credits [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives			1	[1]
Level 2 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	47		44
Level 2 [Member] | Other Current Liabilities [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	24	[1]	23	[1]
Level 2 [Member] | Other Noncurrent Liabilities And Deferred Credits [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	23	[1]	21	[1]
Level 3 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	712		630
Level 3 [Member] | Other Current Liabilities [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	38		32
Level 3 [Member] | Other Noncurrent Liabilities And Deferred Credits [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	636		570
Level 3 [Member] | Other Noncurrent Liabilities And Deferred Credits [Member] | Derivatives Designated As Hedging Instruments [Member] | Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	10
Level 3 [Member] | Other Noncurrent Liabilities And Deferred Credits [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Embedded Credit Derivative [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value liability derivatives	$ 28	[1]	$ 28	[1]

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

[2] All margin posted is in the form of cash and is valued under a Level 1 technique. The levels that correspond to the margin posted in the table above reference the level of the corresponding liability for which it is posted. Alcoa elected to net the margin posted against the fair value amounts recognized for derivative instruments executed with the same counterparties under master netting arrangements.