XML 55 R42.htm IDEA: XBRL DOCUMENT
v3.8.0.1

Revenue from Contracts with Customers - Narrative (Details) | 3 Months Ended
--- | ---
Mar. 31, 2018
Revenue from Contract with Customer [Abstract] |
Revenue, shipping payment terms | 30 days

X
- Definition Revenue, Terms Of Payment, Period + References No definition available. + Details
Name: | arnc_RevenueTermsOfPaymentPeriod
Namespace Prefix: | arnc_
Data Type: | xbrli:durationItemType
Balance Type: | na
Period Type: | duration

X
- References No definition available. + Details
Name: | us-gaap_RevenueFromContractWithCustomerAbstract
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration