XML 64 R52.htm IDEA: XBRL DOCUMENT
v3.7.0.1

Pension and Other Postretirement Benefits - Additional Information (Detail) |  | 3 Months Ended
--- | --- | ---
Apr. 18, 2017 USD ($) | Mar. 31, 2017 USD ($) Installments
Defined Benefit Plan Disclosure [Line Items] |  |
Cash contribution term to pension plan |  | 30 months
Number of installments | Installments |  | 3
Minimum required cash contribution to pension plan |  | $ 50,000,000
Aggregate cash cash contribution to pension plan |  | $ 150,000,000
Subsequent Event [Member] |  |
Defined Benefit Plan Disclosure [Line Items] |  |
First payment to pension plan | $ 50,000,000 |

X
- Definition Aggregate cash contribution to pension plan. + References No definition available. + Details
Name: | arnc_AggregateCashContributionToPensionPlan
Namespace Prefix: | arnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Cash contribution term to pension plan. + References No definition available. + Details
Name: | arnc_CashContributionTermToPensionPlan
Namespace Prefix: | arnc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- Definition Minimum required cash contribution to pension plan. + References No definition available. + Details
Name: | arnc_MinimumRequiredCashContributionToPensionPlan
Namespace Prefix: | arnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Number of installment made for cash contribution to pension plan. + References No definition available. + Details
Name: | arnc_NumberOfInstallmentMadeForCashContributionToPensionPlan
Namespace Prefix: | arnc_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | duration

X
- Definition Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table. + References No definition available. + Details
Name: | us-gaap_DefinedBenefitPlanDisclosureLineItems
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition The amount of cash or cash equivalents contributed during the reporting period by the entity to fund its pension plans and its non-pension postretirement benefit plans. + References Reference 1: http://www.xbrl.org/2003/role/presentationRef -Publisher FASB -Name Accounting Standards Codification -Topic 230 -SubTopic 10 -Section 45 -Paragraph 25 -Subparagraph (g) -URI http://asc.fasb.org/extlink&oid=66902209&loc=d3e3536-108585 + Details
Name: | us-gaap_PensionAndOtherPostretirementBenefitContributions
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Details
Name: | us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |