Income Taxes - Reconciliation of U.S. Federal Statutory Rate to Alcoa's Effective Tax Rate for Continuing Operations (Detail)	12 Months Ended
	Dec. 31, 2013	Dec. 31, 2012	Dec. 31, 2011
Income Tax Disclosure [Abstract]
U.S. federal statutory rate	35.00%	35.00%	35.00%
Taxes on foreign operations	(0.30%)	(0.10%)	(11.00%)
Permanent differences on restructuring and other charges and asset disposals	(0.80%)	10.80%
Audit and other adjustments to prior years' accruals	(0.90%)	3.50%	(1.10%)
Noncontrolling interests	(3.10%)	3.80%	0.80%
Statutory tax rate and law changes	0.60%	(0.40%)	0.80%
Changes in valuation allowances	(23.20%)	15.20%	2.30%
Impairment of goodwill	(33.30%)
Amortization of goodwill related to intercompany stock sales/reorganizations	1.10%	(7.70%)	(2.80%)
Change in legal structure of investment		(4.10%)
Interest income related to income tax positions		(1.30%)	(0.20%)
Company-owned life insurance/split-dollar net premiums	1.10%	(3.90%)	(0.20%)
Other	0.20%	(0.80%)	0.40%
Effective tax rate	(23.60%)	50.00%	24.00%