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Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive Loss by Component (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2015 | Sep. 30, 2014 | Sep. 30, 2015 | Sep. 30, 2014
Pension and other postretirement benefits |  |  |  |
Total Other comprehensive income (loss) | $ 120 | $ 122 | $ 226 | $ 214
Foreign currency translation |  |  |  |
Other comprehensive loss | (1,188) | (1,000) | (2,166) | (464)
Available-for-sale securities |  |  |  |
Other comprehensive (loss) income | (2) | (1) | (2) |
Cash flow hedges |  |  |  |
Total Other comprehensive income (loss) | 215 | (14) | 581 | (11)
Energy Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Total Other comprehensive income (loss) before reclassifications, net of tax | 3 | (28) | (8) | (10)
Alcoa [Member] |  |  |  |
Pension and other postretirement benefits |  |  |  |
Balance at beginning of period | (3,500) | (3,441) | (3,601) | (3,532)
Unrecognized net actuarial loss and prior service cost/benefit | 46 | 96 | (30) | 33
Tax (expense) benefit | (10) | (33) | 18 | (8)
Total Other comprehensive (loss) income before reclassifications, net of tax | 36 | 63 | (12) | 25
Amortization of net actuarial loss and prior service cost/benefit | 116 | 97 | 345 | 296
Tax expense | (41) | (34) | (121) | (104)
Total amount reclassified from Accumulated other comprehensive loss, net of tax | 75 | 63 | 224 | 192
Total Other comprehensive income (loss) | 111 | 126 | 212 | 217
Balance at end of period | (3,389) | (3,315) | (3,389) | (3,315)
Foreign currency translation |  |  |  |
Balance at beginning of period | (1,606) | 569 | (846) | 179
Other comprehensive loss | (889) | (774) | (1,649) | (384)
Balance at end of period | (2,495) | (205) | (2,495) | (205)
Available-for-sale securities |  |  |  |
Balance at beginning of period |  | 3 |  | 2
Other comprehensive (loss) income | (2) | (1) | (2) |
Balance at end of period | (2) | 2 | (2) | 2
Cash flow hedges |  |  |  |
Balance at beginning of period | 140 | (299) | (230) | (308)
Net change from periodic revaluations | 288 | (35) | 792 | (31)
Tax (expense) benefit | (79) | 11 | (235) | 7
Total Other comprehensive income (loss) before reclassifications, net of tax | 209 | (24) | 557 | (24)
Net amount reclassified to earnings | 6 | 6 | 35 | 17
Tax expense | (1) | (1) | (8) | (3)
Total amount reclassified from Accumulated other comprehensive income (loss), net of tax | 5 | 5 | 27 | 14
Total Other comprehensive income (loss) | 214 | (19) | 584 | (10)
Balance at end of period | 354 | (318) | 354 | (318)
Alcoa [Member] | Aluminum Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings | 3 | 7 | 26 | 18
Alcoa [Member] | Energy Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings |  |  | 4 |
Alcoa [Member] | Foreign Exchange Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings | 2 | (1) | 3 | (2)
Alcoa [Member] | Interest Rate Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings |  |  | 1 | 1
Alcoa [Member] | Nickel Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings | 1 |  | 1 |
Noncontrolling Interests [Member] |  |  |  |
Pension and other postretirement benefits |  |  |  |
Balance at beginning of period | (59) | (50) | (64) | (51)
Unrecognized net actuarial loss and prior service cost/benefit | 10 | (9) | 13 | (9)
Tax (expense) benefit | (1) | 3 | (1) | 3
Total Other comprehensive (loss) income before reclassifications, net of tax | 9 | (6) | 12 | (6)
Amortization of net actuarial loss and prior service cost/benefit |  | 3 | 4 | 5
Tax expense |  | (1) | (2) | (2)
Total amount reclassified from Accumulated other comprehensive loss, net of tax |  | 2 | 2 | 3
Total Other comprehensive income (loss) | 9 | (4) | 14 | (3)
Balance at end of period | (50) | (54) | (50) | (54)
Foreign currency translation |  |  |  |
Balance at beginning of period | (569) | 36 | (351) | (110)
Other comprehensive loss | (299) | (226) | (517) | (80)
Balance at end of period | (868) | (190) | (868) | (190)
Cash flow hedges |  |  |  |
Balance at beginning of period | (6) | (8) | (2) | (2)
Net change from periodic revaluations | 1 | 7 | (4) | (2)
Tax (expense) benefit |  | (2) | 1 | 1
Total Other comprehensive income (loss) before reclassifications, net of tax | 1 | 5 | (3) | (1)
Total Other comprehensive income (loss) | 1 | 5 | (3) | (1)
Balance at end of period | $ (5) | $ (3) | $ (5) | $ (3)

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- Definition The total of net gain (loss), prior service cost (credit), and transition assets (obligations), as well as minimum pension liability if still remaining, included in accumulated other comprehensive income associated with a defined benefit pension or other postretirement plan(s) because they have yet to be recognized as components of net periodic benefit cost. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (j-k) -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669646-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 11 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e637-108580 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14 -URI http://asc.fasb.org/extlink&oid=36458714&loc=d3e681-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 715 -SubTopic 20 -Section 50 -Paragraph 1 -Subparagraph (i) -URI http://asc.fasb.org/extlink&oid=58740216&loc=d3e1928-114920 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 14A -URI http://asc.fasb.org/extlink&oid=36458714&loc=SL7669686-108580 + Details
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