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1122 - Disclosure - Income Taxes - Reconciliation of U.S. Federal Statutory Rate to Alcoa's Effective Tax Rate for Continuing Operations (Detail)
(http://www.alcoa.com/taxonomy/role/DisclosureIncomeTaxesReconciliationOfUSFederalStatutoryRateToAlcoasEffectiveTaxRateForContinuingOperations)
TableReconciliation Of Effective Income Tax Rate [Table]
Slicers (applies to each fact value in each table cell)
Income Taxes [Line Items]Period [Axis]
2012-01-01 - 2012-12-31
2011-01-01 - 2011-12-31
2010-01-01 - 2010-12-31
U.S. federal statutory rate
0.35  
0.35  
0.35  
Taxes on foreign operations
(.001) 
(.110) 
(.054) 
Permanent differences on restructuring charges and asset disposals
.108  
 
.007  
Audit and other adjustments to prior years' accruals
.035  
(.011) 
.012  
Noncontrolling interests
.038  
.008  
.026  
Statutory tax rate and law changes
(.004) 
.008  
(.051) 
Tax law change related to Medicare Part D
 
 
.144  
Changes in valuation allowances
.152  
.023  
(.087) 
Amortization of goodwill related to intercompany stock sales/reorganizations
(.077) 
(.028) 
(.052) 
Change in legal structure of investment
(.041) 
 
 
Interest income related to income tax positions
(.013) 
(.002) 
 
Company-owned life insurance/split-dollar net premiums
(.039) 
(.002) 
(.018) 
Other
(.008) 
.004  
(.008) 
Effective tax rate
.500  
 
.240  
 
.269