XML 94 R74.htm IDEA: XBRL DOCUMENT
v3.22.0.1

Other Expense, Net - Narrative (Details) € in Millions, $ in Millions | Dec. 31, 2020 USD ($) | Dec. 31, 2020 EUR (€)
--- | --- | ---
Alcoa Corporation |  |
Other Non operating Income Expense [Line Items] |  |
Tax agreement, indemnification of ultimate liability, percent | 49.00% | 49.00%
Spain |  |
Other Non operating Income Expense [Line Items] |  |
Income taxes receivable | $ 53 | € 45
Tax agreement, indemnification of ultimate liability, percent | 33.66% | 33.66%

X
- Definition Other Non operating Income Expense [Line Items] + References No definition available. + Details
Name: | hwm_OtherNonOperatingIncomeExpenseLineItems
Namespace Prefix: | hwm_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Definition Tax Agreement, Indemnification Of Ultimate Liability, Percent + References No definition available. + Details
Name: | hwm_TaxAgreementIndemnificationOfUltimateLiabilityPercent
Namespace Prefix: | hwm_
Data Type: | dtr-types:percentItemType
Balance Type: | na
Period Type: | instant

X
- Definition Carrying amount as of the balance sheet date of income taxes previously overpaid to tax authorities (such as U.S. Federal, state and local tax authorities) representing refunds of overpayments or recoveries based on agreed-upon resolutions of disputes. Also called income tax refund receivable. + References Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 210 -SubTopic 10 -Section S99 -Paragraph 1 -Subparagraph (SX 210.5-02(8)) -URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682 Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef -Publisher FASB -Name Accounting Standards Codification -Topic 944 -SubTopic 210 -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(10)) -URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910 + Details
Name: | us-gaap_IncomeTaxReceivable
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Details
Name: | us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=hwm_AlcoaCorporationMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | srt_StatementGeographicalAxis=country_ES
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |