Derivatives And Other Financial Instruments (Schedule Of Fair Values Of Outstanding Derivative Contracts Recorded As Assets) (Details) (USD $) In Millions, unless otherwise specified	Mar. 31, 2012		Dec. 31, 2011
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	$ 81		$ 94
Derivatives Designated As Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	93		109
Derivatives Not Designated As Hedging Instruments [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	6	[1]	7	[1]
Other Noncurrent Assets [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	18	[2]	22	[2]
Level 1 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	46		57
Level 1 [Member] | 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	39		51
Level 1 [Member] | Prepaid Expenses And Other Current Assets [Member] | Margin Held [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives			7	[2]
Level 1 [Member] | Other Noncurrent Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	6		6
Level 1 [Member] | 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	[1]
Level 2 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	45		47
Level 2 [Member] | 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	5		8
Level 2 [Member] | 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]	1	[1]
Level 2 [Member] | Prepaid Expenses And Other Current Assets [Member] | Margin Held [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	5	[2]	8	[2]
Level 2 [Member] | Other Noncurrent Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	39		37
Level 2 [Member] | Other Noncurrent Assets [Member] | Margin Held [Member] | Interest Rate Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	13	[2]	7	[2]
Level 3 [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	8		12
Level 3 [Member] | 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	4		5
Level 3 [Member] | Other Noncurrent Assets [Member] | Derivatives Designated As Hedging Instruments [Member] | Energy Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives			2
Level 3 [Member] | Other Noncurrent Assets [Member] | Derivatives Not Designated As Hedging Instruments [Member] | Aluminum Contracts [Member]
Derivative Instruments, Gain (Loss) [Line Items]
Fair value asset derivatives	$ 4	[1]	$ 5	[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 held is in the form of cash and is valued under a Level 1 technique. The levels that correspond to the margin held in the table above reference the level of the corresponding asset for which it is held. Alcoa elected to net the margin held against the fair value amounts recognized for derivative instruments executed with the same counterparties under master netting arrangements.