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Debt (Credit Facilities) (Detail) - USD ($) |  | 12 Months Ended |
--- | --- | --- | ---
Jul. 25, 2014 | Dec. 31, 2017 | Dec. 31, 2016 | Dec. 31, 2015 | Sep. 30, 2016
Debt Instrument [Line Items] |  |  |  |  |
Ratio of indebtedness to consolidated EBITDA |  | 4.50% |  |  |
Ratio of indebtedness to consolidated EBITDA, after December 31, 2019 |  | 3.50% |  |  |
Extension of maturity period |  | 1 year |  |  |
Maximum borrowing capacity |  | $ 715,000,000 |  |  |
Arconic |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Line of credit facility, repayment |  | $ 810,000,000 | $ 1,950,000,000 | $ 1,890,000,000 |
Weighted-average interest rate |  | 2.60% | 1.90% | 1.60% |
Weighted-average maturity days |  | 46 days | 49 days | 69 days |
Maximum |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Applicable margin on LIBOR loans |  | 1.70% |  |  |
Minimum |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Applicable margin on LIBOR loans |  | 0.70% |  |  |
Revolving Credit Agreement |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Revolving credit facility, term | 5 years |  |  |  |
Revolving Credit Agreement | Prior to Amendment |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Line of credit facility, outstanding borrowings | $ 4,000,000,000 |  |  |  |
Revolving Credit Agreement | After Amendment |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Line of credit facility, outstanding borrowings |  |  |  |  | $ 3,000,000,000
Commercial Paper | Maximum |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Fees paid to maintain credit facility |  | 0.30% |  |  |
Senior Unsecured Revolving Credit Facility |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Line of credit facility, outstanding borrowings |  | $ 0 | $ 0 |  |
Amounts borrowed under the credit agreement |  | 0 | $ 0 | $ 0 |
Expected Maturity Date Year 2017 |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Maximum borrowing capacity |  | 640,000,000 |  |  |
Expected Maturity Date Year 2018 |  |  |  |  |
Debt Instrument [Line Items] |  |  |  |  |
Maximum borrowing capacity |  | $ 75,000,000 |  |  |

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- Definition Applicable margin on LIBOR loans. + References No definition available. + Details
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- Definition Debt covenants net leverage ratio. + References No definition available. + Details
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- Definition Debt covenants net leverage ratio after year three. + References No definition available. + Details
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- Definition Line of credit facility, term. + References No definition available. + Details
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- Definition Weighted average interest rate, outstanding borrowings. + References No definition available. + Details
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- Definition The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(22)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 Reference 2: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(16)) -URI http://asc.fasb.org/extlink&oid=6879938&loc=d3e572229-122910 Reference 3: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 942 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.9-03(16)) -URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878 + Details
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- Definition The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used. + References No definition available. + Details
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- Definition Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02.19(b),22(b)) -URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682 + Details
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- Definition The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 14 -Subparagraph (b) -URI http://asc.fasb.org/extlink&oid=98514028&loc=d3e3255-108585 + Details
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