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Recently Adopted and Recently Issued Accounting Guidance - Summary of Changes in Accumulated Other Comprehensive Loss by Component (Detail) (USD $)
In Millions, unless otherwise specified
 3 Months Ended
Mar. 31, 2013
Mar. 31, 2012
Other comprehensive income:    
Total Other comprehensive income $ 96 $ 58
Other comprehensive (loss) income:    
Foreign currency translation adjustments (100) 309
Other comprehensive income:    
Total Other comprehensive income 1 2
Net amount reclassified to earnings:    
Total Other comprehensive income (loss) 115 (83)
Alcoa [Member]
    
Pension and other postretirement benefits    
Balance at beginning of period (4,063) (3,533)
Other comprehensive income:    
Unrecognized net actuarial loss and prior service cost/benefit 11 (13)
Tax (expense) benefit (3) 3
Total Other comprehensive income before reclassifications, net of tax 8 (10)
Amortization of net actuarial loss and prior service cost/benefit 132 101
Tax (expense) benefit (45) (35)
Total amount reclassified from Accumulated other comprehensive loss, net of tax 87 66
Total Other comprehensive income 95 56
Balance at end of period (3,968) (3,477)
Foreign currency translation    
Balance at beginning of period 1,147 1,349
Other comprehensive (loss) income:    
Foreign currency translation adjustments (116) 244
Balance at end of period 1,031 1,593
Available-for-sale securities    
Balance at beginning of period 3  
Other comprehensive income:    
Net unrealized holding (loss) gain (1) 3
Tax benefit (expense)   (1)
Total Other comprehensive (loss) income before reclassifications, net of tax (1) 2
Net amount reclassified to earnings 2  
Tax benefit (expense)      
Total amount reclassified from Accumulated other comprehensive income, net of tax 2  
Total Other comprehensive income 1 2
Balance at end of period 4 2
Cash flow hedges    
Balance at beginning of period (489) (443)
Other comprehensive income (loss):    
Net change from periodic revaluations 136 (103)
Tax (expense) benefit (29) 21
Total Other comprehensive income (loss) before reclassifications, net of tax 107 (82)
Net amount reclassified to earnings:    
Net amount reclassified to earnings 7 (1)
Tax (expense) benefit (1) 2
Total amount reclassified from Accumulated other comprehensive loss, net of tax 6 1
Total Other comprehensive income (loss) 113 (81)
Balance at end of period (376) (524)
Alcoa [Member] | Aluminum contracts [Member]
    
Net amount reclassified to earnings:    
Net amount reclassified to earnings 7  
Alcoa [Member] | Interest rate contracts [Member]
    
Net amount reclassified to earnings:    
Net amount reclassified to earnings   (1)
Noncontrolling Interests [Member]
    
Pension and other postretirement benefits    
Balance at beginning of period (77) (99)
Other comprehensive income:    
Amortization of net actuarial loss and prior service cost/benefit 1 2
Tax (expense) benefit 0 0
Total amount reclassified from Accumulated other comprehensive loss, net of tax 1 2
Total Other comprehensive income 1 2
Balance at end of period (76) (97)
Foreign currency translation    
Balance at beginning of period 257 351
Other comprehensive (loss) income:    
Foreign currency translation adjustments 16 65
Balance at end of period 273 416
Other comprehensive income:    
Tax benefit (expense)      
Cash flow hedges    
Balance at beginning of period (5) (4)
Other comprehensive income (loss):    
Net change from periodic revaluations 3 (3)
Tax (expense) benefit (1) 1
Total Other comprehensive income (loss) before reclassifications, net of tax 2 (2)
Net amount reclassified to earnings:    
Total Other comprehensive income (loss) 2 (2)
Balance at end of period $ (3) $ (6)