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Accumulated Other Comprehensive Loss - Summary of Changes in Accumulated Other Comprehensive (Loss) Income by Component (Detail) - USD ($) $ in Millions | 3 Months Ended | 9 Months Ended
--- | --- | ---
Sep. 30, 2016 | Sep. 30, 2015 | Sep. 30, 2016 | Sep. 30, 2015
Pension and other postretirement benefits |  |  |  |
Total Other comprehensive (loss) income | $ (463) | $ 120 | $ (363) | $ 226
Foreign currency translation |  |  |  |
Other comprehensive income (loss) | 202 | (1,188) | 689 | (2,166)
Available-for-sale securities |  |  |  |
Other comprehensive income (loss) |  | (2) | 4 | (2)
Cash flow hedges |  |  |  |
Total Other comprehensive (loss) income | (348) | 215 | (567) | 581
Energy Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Total Other comprehensive (loss) income before reclassifications, net of tax | 49 | 3 | 88 | (8)
Arconic [Member] |  |  |  |
Pension and other postretirement benefits |  |  |  |
Balance at beginning of period | (3,514) | (3,500) | (3,611) | (3,601)
Unrecognized net actuarial loss and prior service cost/benefit | (819) | 46 | (883) | (30)
Tax benefit (expense) | (286) | 10 | 312 | 18
Total Other comprehensive (loss) income before reclassifications, net of tax | (533) | 36 | (571) | (12)
Amortization of net actuarial loss and prior service cost/benefit | 109 | 116 | 317 | 345
Tax expense | (38) | (41) | (111) | (121)
Total amount reclassified from Accumulated other comprehensive loss, net of tax | 71 | 75 | 206 | 224
Total Other comprehensive (loss) income | (462) | 111 | (365) | 212
Balance at end of period | (3,976) | (3,389) | (3,976) | (3,389)
Foreign currency translation |  |  |  |
Balance at beginning of period | (2,064) | (1,606) | (2,412) | (846)
Other comprehensive income (loss) | 157 | (889) | 505 | (1,649)
Balance at end of period | (1,907) | (2,495) | (1,907) | (2,495)
Available-for-sale securities |  |  |  |
Balance at beginning of period | (1) |  | (5) |
Other comprehensive income (loss) |  | (2) | 4 | (2)
Balance at end of period | (1) | (2) | (1) | (2)
Cash flow hedges |  |  |  |
Balance at beginning of period | 364 | 140 | 597 | (230)
Net change from periodic revaluations | (430) | 288 | (772) | 792
Tax benefit (expense) | 126 | (79) | 229 | (235)
Total Other comprehensive (loss) income before reclassifications, net of tax | (304) | 209 | (543) | 557
Net amount reclassified to earnings | (46) | 6 | (41) | 35
Tax benefit (expense) | 12 | (1) | 13 | (8)
Total amount reclassified from Accumulated other comprehensive (loss) income, net of tax | (34) | 5 | (28) | 27
Total Other comprehensive (loss) income | (338) | 214 | (571) | 584
Balance at end of period | 26 | 354 | 26 | 354
Arconic [Member] | Aluminum Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings | 5 | 3 | (1) | 26
Arconic [Member] | Energy Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings | (50) |  | (49) | 4
Arconic [Member] | Foreign Exchange Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings | (1) | 2 |  | 3
Arconic [Member] | Interest Rate Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings |  |  | 8 | 1
Arconic [Member] | Nickel Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings |  | 1 | 1 | 1
Noncontrolling Interests [Member] |  |  |  |
Pension and other postretirement benefits |  |  |  |
Balance at beginning of period | (53) | (59) | (56) | (64)
Unrecognized net actuarial loss and prior service cost/benefit | (1) | 10 |  | 13
Tax benefit (expense) |  | 1 |  | (1)
Total Other comprehensive (loss) income before reclassifications, net of tax | (1) | 9 |  | 12
Amortization of net actuarial loss and prior service cost/benefit | 1 |  | 3 | 4
Tax expense | (1) |  | (1) | (2)
Total amount reclassified from Accumulated other comprehensive loss, net of tax |  |  | 2 | 2
Total Other comprehensive (loss) income | (1) | 9 | 2 | 14
Balance at end of period | (54) | (50) | (54) | (50)
Foreign currency translation |  |  |  |
Balance at beginning of period | (641) | (569) | (780) | (351)
Other comprehensive income (loss) | 45 | (299) | 184 | (517)
Balance at end of period | (596) | (868) | (596) | (868)
Cash flow hedges |  |  |  |
Balance at beginning of period | 11 | (6) | (3) | (2)
Net change from periodic revaluations | 20 | 1 | 35 | (4)
Tax benefit (expense) | (6) |  | (10) | 1
Total Other comprehensive (loss) income before reclassifications, net of tax | 14 | 1 | 25 | (3)
Net amount reclassified to earnings | (34) |  | (29) |
Tax benefit (expense) | 10 |  | 8 |
Total amount reclassified from Accumulated other comprehensive (loss) income, net of tax | (24) |  | (21) |
Total Other comprehensive (loss) income | (10) | 1 | 4 | (3)
Balance at end of period | 1 | $ (5) | 1 | $ (5)
Noncontrolling Interests [Member] | Energy Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings | $ (34) |  | (34) |
Noncontrolling Interests [Member] | Interest Rate Contracts [Member] |  |  |  |
Cash flow hedges |  |  |  |
Net amount reclassified to earnings |  |  | $ 5 |

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- Definition Accumulated appreciation or loss, net of tax, in value of the total of available-for-sale securities at the end of an accounting period. + References Reference 1: 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=66004124&loc=SL7669686-108580 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=66004124&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=66004124&loc=d3e681-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (e) -URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669646-108580 + Details
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- Definition Accumulated change, net of tax, in accumulated gains and losses from derivative instruments designated and qualifying as the effective portion of cash flow hedges. Includes an entity's share of an equity investee's Increase or Decrease in deferred hedging gains or losses. + 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 (d) -URI http://asc.fasb.org/extlink&oid=66004124&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=66004124&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 14A -URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669686-108580 Reference 4: 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=66004124&loc=d3e681-108580 Reference 5: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 815 -SubTopic 30 -Section 50 -Paragraph 2 -URI http://asc.fasb.org/extlink&oid=35736893&loc=d3e80784-113994 + Details
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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=66004124&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=66004124&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=66004124&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=65897934&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=66004124&loc=SL7669686-108580 + Details
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- Definition Accumulated adjustment, net of tax, that results from the process of translating subsidiary financial statements and foreign equity investments into the reporting currency from the functional currency of the reporting entity, net of reclassification of realized foreign currency translation gains or losses. + References Reference 1: 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=66004124&loc=d3e681-108580 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 220 -SubTopic 10 -Section 45 -Paragraph 10A -Subparagraph (a) -URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669646-108580 Reference 3: 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=66004124&loc=d3e637-108580 Reference 4: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 45 -Paragraph 12 -URI http://asc.fasb.org/extlink&oid=64808268&loc=d3e32022-110900 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=66004124&loc=SL7669686-108580 Reference 6: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 830 -SubTopic 30 -Section 50 -Paragraph 1 -URI http://asc.fasb.org/extlink&oid=6450520&loc=d3e32583-110901 + Details
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- Definition Amount after tax and reclassification adjustments, of appreciation (loss) in value of unsold available-for-sale securities. Excludes amounts related to other than temporary impairment (OTTI) loss. + 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 (e) -URI http://asc.fasb.org/extlink&oid=66004124&loc=SL7669646-108580 + Details
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