Contingencies and Commitments - Additional Information (Detail) In Millions, unless otherwise specified	1 Months Ended		3 Months Ended		6 Months Ended		12 Months Ended				1 Months Ended						3 Months Ended				1 Months Ended		3 Months Ended			6 Months Ended			1 Months Ended
	Nov. 28, 2011	Jun. 30, 2009	Jun. 30, 2013 USD ($) Kmt	Jun. 30, 2012 USD ($)	Jun. 30, 2013 USD ($) Kmt	Jun. 30, 2012 USD ($)	Dec. 31, 2012 USD ($) Installment	Dec. 31, 2012 EUR (€)	Mar. 31, 2013 USD ($)	Mar. 31, 2013 EUR (€)	Nov. 30, 2006 Curtis v. Alcoa Inc. [Member] Person	Jun. 30, 2013 Minimum [Member] USD ($)	Jun. 30, 2013 Maximum [Member] USD ($)	Jun. 30, 2013 Maximum [Member] EUR (€)	Feb. 21, 2013 Alcoa Trasformazioni [Member] USD ($)	Feb. 21, 2013 Alcoa Trasformazioni [Member] EUR (€)	Jun. 30, 2013 Alcoa [Member] USD ($)	Jun. 30, 2013 Alcoa [Member] EUR (€)	Jun. 30, 2013 Alumina [Member]	Jun. 30, 2013 Aluminium Bahrain [Member] USD ($)	Oct. 09, 2012 Alba [Member] USD ($)	Feb. 27, 2008 Alba [Member]	Jun. 30, 2013 Alba [Member]	Sep. 30, 2012 Alba [Member] USD ($)	Jun. 30, 2012 Alba [Member] USD ($)	Jun. 30, 2013 Alba [Member] USD ($)	Jun. 30, 2013 Alba [Member] Minimum [Member] USD ($)	Jun. 30, 2013 Alba [Member] Maximum [Member] USD ($)	Jul. 31, 2006 Italian Government [Member]	Nov. 19, 2009 Italian Government [Member] USD ($)	Nov. 19, 2009 Italian Government [Member] EUR (€)
Loss Contingencies [Line Items]
Period of alleged conspiracy, years																						15 years
Damages claimed, value																										$ 1,000
Number of days required to dismiss lawsuit	30 days
Cash payment for suit settlement																				103				40	45
Restructuring and other charges			244	15	251	25														103					45
Restructuring and other charges, after-tax and noncontrolling interests			170	10	175	17														62				15	18
Estimated additional reasonably possible charge							395	303												200					75
Contingency settlement agreement amount, total																					85
Contingency settlement agreement amount paid																					42.5
Contingency settlement agreement amount payable																					42.5
Contingency settlement agreement future payable date																							October 9, 2013
Percentage of equity interest																							40.00%
Estimated contingency settlement changes, net of tax																											25	30
Estimated additional reasonably possible charge, minimum							207	159												0
Amount of settlement offer rejected			60
Charges recorded of settlement amount			0
Percentage of allocated Cost of settlement																	85.00%	85.00%	15.00%
Cash payment for suit settlement																				25
Retired former employees involved in class action											13,000
Trial length, number of days		8 days
Management estimate for maximum exposure from class action									110	85					97	76
Provision for contract losses												0	97	76
Number of years operating under a power supply structure																													10 years
Charge related to European Commission announcement																														250	173
Write-off of receivable																														20	14
Establishment reserve																														230	159
Recovery amount							375	303
Reduction in recovery amount							65	53
Payments to Italian Government							310	250
Payments to Italian Government, installments amount							65	50
Number of installments, litigation payment							5	5
Litigation reserve							$ 207	€ 159									$ 11	€ 9
Amount of curtailment, in kmt-per-year			44		44