Debt - Additional Information (Detail) (USD $) In Millions, except Per Share data, unless otherwise specified	3 Months Ended
	Mar. 31, 2014
Alcoa [Member]
Debt Instrument [Line Items]
Line of credit facility, borrowing	$ 620
Line of credit facility, repayment	620
Weighted-average interest rate	1.53%
Weighted-average maturity days	49 days
Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Number of revolving credit facility agreements	10
Outstanding borrowings	1,190
Revolving credit facility term	5 years
Revolving credit facility term start	2014-02
Revolving credit facility term end	2015-12
Revolving Credit Facility [Member] | First Loans Agreement [Member]
Debt Instrument [Line Items]
Outstanding borrowings	150
Line of credit facility, expiration date	2014-02
Extended credit facility maturity date	2015-03
Revolving Credit Facility [Member] | Second Loans Agreement [Member]
Debt Instrument [Line Items]
Outstanding borrowings	150
Line of credit facility, expiration date	2014-03
Line of credit facility, new agreement date	2014-04
Revolving Credit Facility [Member] | Eleventh Revolving Credit Facility Agreement [Member]
Debt Instrument [Line Items]
Outstanding borrowings	50
Line of credit facility, expiration date	2016-02
5.25% Convertible Notes, Due 2014 [Member]
Debt Instrument [Line Items]
Principal amount of convertible notes	$ 575
Convertible notes, interest rate	5.25%
Convertible notes due date	Mar. 15, 2014
Number of shares, option exercised	89
Conversion rate, numerator	155.4908
Conversion rate, denominator	$ 1,000
Convertible notes, conversion price	$ 6.43
Par value of issued shares	$ 89