Debt - Additional Information (Detail) In Millions, unless otherwise specified	1 Months Ended		12 Months Ended							12 Months Ended										12 Months Ended					12 Months Ended		12 Months Ended		1 Months Ended			1 Months Ended		1 Months Ended					12 Months Ended				12 Months Ended
	May 31, 2013 USD ($)	Aug. 31, 2012	Dec. 31, 2013 USD ($) Agreement LetterOfCredit	Dec. 31, 2013 BRL	Dec. 31, 2012 USD ($)	Dec. 31, 2012 BRL	Dec. 31, 2011 USD ($)	Jan. 31, 2012	Jul. 25, 2011 USD ($)	Dec. 31, 2013 Minimum [Member]	Dec. 31, 2013 Maximum [Member]	Dec. 31, 2013 Aluminio [Member] USD ($)	Dec. 31, 2013 Aluminio [Member] BRL	Dec. 31, 2012 Aluminio [Member] USD ($)	Dec. 31, 2013 Alcoa [Member] USD ($)	Dec. 31, 2012 Alcoa [Member] USD ($)	Dec. 31, 2013 Credit Facility [Member] USD ($)	Dec. 31, 2012 Credit Facility [Member] USD ($)	Dec. 31, 2013 Revolving Credit Facility Excluding Commercial Paper [Member] USD ($)	Dec. 31, 2013 Loan Agreement with BNDES [Member] Agreement	Dec. 31, 2012 Loan Agreement with BNDES [Member]	Dec. 31, 2013 Commercial Paper [Member] USD ($)	Dec. 31, 2012 Commercial Paper [Member] USD ($)	Dec. 31, 2011 Commercial Paper [Member]	Dec. 31, 2013 Revolving Credit Agreement [Member]	Dec. 31, 2012 Two term loans agreements [Member] USD ($)	Dec. 31, 2013 First Loans Agreement [Member] Revolving Credit Facility Excluding Commercial Paper [Member] USD ($)	Dec. 31, 2013 Second Loans Agreement [Member] Revolving Credit Facility Excluding Commercial Paper [Member] USD ($)	May 31, 2013 6.00% Notes, Due 2013 [Member] USD ($)	Dec. 31, 2013 6.00% Notes, Due 2013 [Member]	Dec. 31, 2012 6.00% Notes, Due 2013 [Member] USD ($)	May 31, 2013 Debt Accrued and Unpaid Interest [Member] USD ($)	Jan. 31, 2012 6.00% Notes, due 2012 [Member] USD ($)	Aug. 31, 2012 Midwestern Disaster Area Revenue Bonds Series 2012 Due 2042 [Member] USD ($)	Dec. 31, 2013 Three of the Subloans [Member] Loan Agreement with BNDES [Member] USD ($)	Dec. 31, 2013 Three of the Subloans [Member] Loan Agreement with BNDES [Member] BRL	Dec. 31, 2013 Two of the Subloans [Member] Loan Agreement with BNDES [Member] BRL	Dec. 31, 2013 Third Subloan [Member] Loan Agreement with BNDES [Member] BRL	Dec. 31, 2013 BNDES Loans, Due 2014-2029 [Member] USD ($) Agreement	Dec. 31, 2013 BNDES Loans, Due 2014-2029 [Member] BRL Agreement	Dec. 31, 2012 BNDES Loans, Due 2014-2029 [Member] USD ($)	Dec. 31, 2012 BNDES Loans, Due 2014-2029 [Member] BRL	Dec. 31, 2012 BNDES First Loans [Member] USD ($)	Dec. 31, 2012 BNDES First Loans [Member] BRL	Dec. 31, 2013 Revolving Credit Facility [Member]	Dec. 31, 2012 Revolving Credit Agreement [Member] Agreement
Debt Instrument [Line Items]
Principal amount of long-term debt maturing in year 2014			$ 658
Principal amount of long-term debt maturing in year 2015			30
Principal amount of long-term debt maturing in year 2016			30
Principal amount of long-term debt maturing in year 2017			778
Principal amount of long-term debt maturing in year 2018			1,046
Aggregate outstanding principal amount																						0	0						422
Interest rate of bonds		4.75%						6.00%																					6.00%	6.00%			6.00%
Payments on long-term debt			2,317		1,489		1,194																						435			12											252	511
Purchase premiums repaid recorded as interest expense	1						(30)
Long-term debt			8,262		8,776																										422		322						325		397
Debt instruments agreement date																																		August 2012
Additional borrowing amount			1	2	7	13																												250
Restricted cash																																		248
Debt instruments maturity date																																		2042
Restricted cash, current			13		171
Debt instrument frequency of periodic payment		Semi-annually
Redemption date of bonds		Alcoa has the option through the loan agreement to redeem the Bonds, as a whole or in part, on or after August 1, 2022, on at least 30 days, but not more than 60 days
Percentage of principal amount repayment		100.00%
Senior debt securities issued under shelf registration statement			1,250		1,250
Commitment on loan agreement			85	177																															397	687
Long-term interest rate																				5.00%	5.00%	0.80%	0.80%	0.80%
Weighted-average margin on long term debt																				1.48%	1.48%
Number of Suloan agreement																				3
Principal and interest																																					667	20
Line of credit facility, outstanding borrowings									3,750			52		280			0	0								350													254	599	311	637
Weighted-average interest rate			6.49%	6.49%	6.49%	6.49%						0.72%	0.72%	2.32%	1.57%	1.89%
Early repayment of outstanding borrowings			22	47	20	38						5	11		1,850	600
Interest rate margin			1.55%	1.55%
Outstanding borrowings			71	166	86	177
Interest rate of outstanding borrowings			6.55%	6.55%	6.55%	6.55%
Combined commitment of loan agreements			200																																				622			1,150
Number of other loan																																							2,000,000	2,000,000
Average outstanding commercial paper																						242	354
Debt instrument maturity date, description																						Matures at various times within one year
Revolving credit facility, term																									5 years
Limit of requested increases in lender commitments			500		990
Letters of credit sublimit under credit facility			1,000
Debt instrument, maturity date																																													July 25, 2016
Extension of maturity period			1 year	1 year
Agreed credit facility amount			3,700
Approved credit facility amount			50
Extended credit facility maturity date			July 25, 2017	July 25, 2017
Fees paid to maintain credit facility																						0.25%
Applicable margin on LIBOR loans										0.50%	1.50%
Amounts borrowed under the credit facility																	0	0
Short-term borrowings			57		53
Accounts payable settlement arrangements			52		48
Number of revolving credit facility agreements																																														6
Termination of revolving credit agreements					(150)
Additional credit arrangements			5	5
Term loan agreement			1	1
Revolving credit agreement			4	4
Outstanding borrowings			700																1,190
Line of credit facility, borrowing															1,850	600
Weighted-average maturity days												70 days	70 days	172 days	213 days	260 days
Revolving credit expiration amount																											$ 1,040	$ 150
Line of credit facility, expiration date																											Dec. 31, 2014	Dec. 31, 2015