Pension And Other Postretirement Benefits (Schedule Of Fair Value Of Pension And Postretirement Plans' Assets) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2011		Dec. 31, 2010
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	$ 10,339	[1]	$ 9,486	[1]
Net payable which represents securities purchased not yet settled less interest and dividends earned on various investments	20		23
Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	2,459	[1]	2,424	[1]
Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	5,120	[1]	5,563	[1]
Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	2,760	[1]	1,499	[1]
Other Investments [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	1,535		1,128
Other Investments [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	295		268
Other Investments [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	74		52
Other Investments [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	1,166		808
Equity Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	3,490	[2]	3,441
Equity Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	941	[2]	1,348
Common stock related to plan contribution	36
Equity Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	1,166	[2]	1,589
Equity Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	1,383	[2]	504
Debt Securities [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	5,314		4,917
Debt Securities [Member] | Level 1 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	1,223		808
Debt Securities [Member] | Level 2 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	3,880		3,922
Debt Securities [Member] | Level 3 [Member]
Defined Benefit Plan Disclosure [Line Items]
Fair value of pension and other postretirement plans' assets	$ 211		$ 187

[1] As of December 31, 2011, the total fair value of pension and other postretirement plans' assets excludes a net payable of $20, which represents securities purchased not yet settled less interest and dividends earned on various investments. As of December 31, 2010, the total fair value of pension and other postretirement plans' assets excludes a net receivable of $23, which represents interest and dividends earned on various investments less securities purchased not yet settled.

[2] At December 31, 2011, Level 1 equity securities include $36 of Alcoa common stock related to the January 2011 plan contribution (see Funding and Cash Flows section below).