Derivatives And Other Financial Instruments (Derivative Contract Assets And Liabilities That Are Measured And Recognized At Fair Value On Recurring Basis) (Details) (USD $) In Millions	Jun. 30, 2011		Dec. 31, 2010
Fair value asset derivatives	$ 108		$ 147
Fair value liability derivatives	904		865
Level 1 [Member]
Fair value asset derivatives	46		76
Level 1 [Member]
Fair value liability derivatives	9		35
Level 2 [Member]
Fair value asset derivatives	40		81
Level 2 [Member]
Fair value liability derivatives	84		83
Level 3 [Member]
Fair value liability derivatives	824		788
Level 3 [Member]
Fair value asset derivatives	28		9
Margin Held [Member]
Fair value asset derivatives	(6)	[1]	(19)	[1]
Margin Posted [Member]
Fair value liability derivatives	(13)	[1]	(41)	[1]
Alcoa [Member]
Fair value asset derivatives	108		147
Fair value liability derivatives	$ 904		$ 865

[1] * Margin held represents cash collateral received related to interest rate contracts included in Level 2 and margin posted represents cash collateral paid related to aluminum contracts included in Level 1 and energy contracts included in Level 3. At December 31, 2010, margin held also represents cash collateral received related to aluminum contracts included in Level 1. Alcoa elected to net the margin held and posted against the fair value amounts recognized for derivative instruments executed with the same counterparties under master netting arrangements.