Cash Flow Information (Schedule Of Cash Paid For Acquisitions) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
Dec. 31, 2011	Dec. 31, 2010	Dec. 31, 2009	Jun. 30, 2009
Cash Flow Information [Abstract]
Assets acquired	$ 253	$ 87	$ 389
Liabilities assumed	(12)	(15)	(294)
Noncontrolling interests acquired		4
Redemption of convertible securities of subsidiary		40
Reduction in Alcoa shareholders' equity		22
Gain recognized			(92)
Cash paid	241	138	3	200
Less: cash acquired	1		115
Net cash paid (received)	$ 240	$ 138	$ (112)

Business Acquisition, Cost Of Acquired Entity, Reduction In Shareholders' Equity

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Payments for acquisitions net of cash acquired

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- Definition

Redemption Of Convertible Securities Of Subsidiary

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Amount of cash paid to acquire the entity.

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Income (expense) and gain (loss) recognized from the settlement of a preexisting relationship between the acquirer and the acquiree.

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The amount of acquisition cost of a business combination allocated to assets acquired.

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The amount of acquisition cost of a business combination allocated to liabilities assumed.

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This element represents the fair value of the noncontrolling interest in the acquiree at the acquisition date.

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The cash inflow associated with the acquisition of business during the period (for example, cash that was held by the acquired business).

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