Debt (Details) (USD $)	1 Months Ended		6 Months Ended
	May 31, 2011	Apr. 30, 2011	Jun. 30, 2011
Amount of public debt offering			$ 515,000,000
Early retirement of outstanding notes		101,000,000
Cash paid for redemption of outstanding debt	972,000,000
Principal amount of debt	881,000,000
Purchase premium	74,000,000
Accrued and unpaid interest	17,000,000
Interest rate swaps, notional amount			550,000,000
Gain on termination of interest rate swaps			33,000,000
Maximum [Member] | 6% Notes, Due 2013 [Member]
Principal amount of debt	400,000,000
Maximum [Member] | 5.4% Notes, Due 2021
Notice period for debt redemption			60.0
Minimum [Member] | 5.4% Notes, Due 2021
Notice period for debt redemption			30.0
5.375% Notes, Due 2013 [Member]
Interest rate on notes issued	5.375%
Debt instrument maturity period	2013
Aggregate outstanding principal amount	269,000,000
Remaining outstanding debt of Alcoa	284,000,000
Interest rate swaps, notional amount			550,000,000
Gain on termination of interest rate swaps			33,000,000
6% Notes, Due 2013 [Member]
Interest rate on notes issued	6.00%
Debt instrument maturity period	2013
Aggregate outstanding principal amount	328,000,000
Remaining outstanding debt	422,000,000
5.4% Notes, Due 2021
Amount of public debt offering		1,250,000,000
Interest rate on notes issued		5.40%
Debt instrument maturity period		2021
Net proceeds from the public debt offering		1,241,000,000
Early retirement of outstanding notes		$ 881,000,000
Repurchase of notes		101.00%