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Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Detail) - USD ($)
$ in Millions
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Dec. 31, 2014
Pension and other postretirement benefits      
Total Other comprehensive (loss) income $ (482) $ (2) $ (82)
Foreign currency translation      
Other comprehensive income (loss) 450 (1,995) (1,266)
Available-for-sale securities      
Other comprehensive income (loss) 137 (5) (2)
Cash flow hedges      
Total Other comprehensive (loss) income (612) 826 78
Arconic [Member]      
Pension and other postretirement benefits      
Balance at beginning of period (3,611) (3,601) (3,532)
Unrecognized net actuarial loss and prior service cost/benefit (1,112) (478) (492)
Tax benefit (expense) 380 170 167
Total Other comprehensive (loss) income before reclassifications, net of tax (732) (308) (325)
Amortization of net actuarial loss and prior service cost/benefit 389 458 394
Tax expense (136) (160) (138)
Total amount reclassified from Accumulated other comprehensive loss, net of tax 253 298 256
Total Other comprehensive (loss) income (479) (10) (69)
Transfer to Alcoa Corporation 2,080    
Balance at end of period (2,010) (3,611) (3,601)
Foreign currency translation      
Balance at beginning of period (2,412) (846) 179
Other comprehensive income (loss) 268 (1,566) (1,025)
Transfer to Alcoa Corporation 1,455    
Balance at end of period (689) (2,412) (846)
Available-for-sale securities      
Balance at beginning of period (5)   2
Other comprehensive income (loss) 137 (5) (2)
Transfer to Alcoa Corporation 0 0 0
Balance at end of period 132 (5)  
Cash flow hedges      
Balance at beginning of period 597 (230) (308)
Net change from periodic revaluations (843) 1,138 78
Tax benefit (expense) 252 (340) (21)
Total Other comprehensive (loss) income before reclassifications, net of tax (591) 798 57
Net amount reclassified to earnings (38) 35 25
Tax benefit (expense) 12 (6) (4)
Total amount reclassified from Accumulated other comprehensive loss, net of tax (26) 29 21
Total Other comprehensive (loss) income (617) 827 78
Transfer to Alcoa Corporation 19    
Balance at end of period (1) 597 (230)
Arconic [Member] | Aluminum Contracts [Member]      
Cash flow hedges      
Net amount reclassified to earnings 1 21 27
Arconic [Member] | Energy Contracts [Member]      
Cash flow hedges      
Net amount reclassified to earnings (49) 6  
Arconic [Member] | Foreign Exchange Contracts [Member]      
Cash flow hedges      
Net amount reclassified to earnings   5 (3)
Arconic [Member] | Interest Rate Contracts [Member]      
Cash flow hedges      
Net amount reclassified to earnings 9 1 1
Arconic [Member] | Nickel Contracts [Member]      
Cash flow hedges      
Net amount reclassified to earnings 1 2  
Noncontrolling Interests [Member]      
Pension and other postretirement benefits      
Balance at beginning of period (56) (64) (51)
Unrecognized net actuarial loss and prior service cost/benefit (9) 5 (22)
Tax benefit (expense) 3 (1) 7
Total Other comprehensive (loss) income before reclassifications, net of tax (6) 4 (15)
Amortization of net actuarial loss and prior service cost/benefit 4 6 3
Tax expense (1) (2) (1)
Total amount reclassified from Accumulated other comprehensive loss, net of tax 3 4 2
Total Other comprehensive (loss) income (3) 8 (13)
Transfer to Alcoa Corporation 59    
Balance at end of period   (56) (64)
Foreign currency translation      
Balance at beginning of period (780) (351) (110)
Other comprehensive income (loss) 182 (429) (241)
Transfer to Alcoa Corporation 596    
Balance at end of period (2) (780) (351)
Available-for-sale securities      
Transfer to Alcoa Corporation 0 0 0
Cash flow hedges      
Balance at beginning of period (3) (2) (2)
Net change from periodic revaluations 36 (1)  
Tax benefit (expense) (10)    
Total Other comprehensive (loss) income before reclassifications, net of tax 26 (1)  
Net amount reclassified to earnings (29)    
Tax benefit (expense) 8    
Total amount reclassified from Accumulated other comprehensive loss, net of tax (21)    
Total Other comprehensive (loss) income 5 (1)  
Transfer to Alcoa Corporation (2)    
Balance at end of period   $ (3) $ (2)
Noncontrolling Interests [Member] | Energy Contracts [Member]      
Cash flow hedges      
Net amount reclassified to earnings (34)    
Noncontrolling Interests [Member] | Interest Rate Contracts [Member]      
Cash flow hedges      
Net amount reclassified to earnings $ 5