v3.22.4

Pension and Other Postretirement Benefits - Fair Value of Plan Assets (Details) - Pension benefits​ - USD ($) $ in Millions	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 1,383	$ 2,124	$ 2,754
Plan Assets
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1,377	2,128
Plan Assets | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	119	130
Plan Assets | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	277	412
Plan Assets | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Plan Assets | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	981	1,586
Equities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	300	652
Equities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1	12
Equities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Equities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Equities | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	299	640
Equity securities
Defined Benefit Plan Disclosure [Line Items]
Plan assets	121	404
Equity securities | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	1	12
Equity securities | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Equity securities | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Equity securities | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	120	392
Long/short equity hedge funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	23	24
Long/short equity hedge funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Long/short equity hedge funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Long/short equity hedge funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Long/short equity hedge funds | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	23	24
Private equity
Defined Benefit Plan Disclosure [Line Items]
Plan assets	156	224
Private equity | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Private equity | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Private equity | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Private equity | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	156	224
Fixed income
Defined Benefit Plan Disclosure [Line Items]
Plan assets	855	1,192
Fixed income | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	118	118
Fixed income | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	277	412
Fixed income | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Fixed income | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	460	662
Intermediate and long duration government/credit
Defined Benefit Plan Disclosure [Line Items]
Plan assets	759	1,119
Intermediate and long duration government/credit | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	113	95
Intermediate and long duration government/credit | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	277	412
Intermediate and long duration government/credit | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Intermediate and long duration government/credit | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	369	612
Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	96	73
Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	5	23
Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Other | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	91	50
Other investments
Defined Benefit Plan Disclosure [Line Items]
Plan assets	222	284
Other investments | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Other investments | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Other investments | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Other investments | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	222	284
Real estate
Defined Benefit Plan Disclosure [Line Items]
Plan assets	93	108
Real estate | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Real estate | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Real estate | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Real estate | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	93	108
Discretionary and systematic macro hedge funds
Defined Benefit Plan Disclosure [Line Items]
Plan assets	100	99
Discretionary and systematic macro hedge funds | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Discretionary and systematic macro hedge funds | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Discretionary and systematic macro hedge funds | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Discretionary and systematic macro hedge funds | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	100	99
Other
Defined Benefit Plan Disclosure [Line Items]
Plan assets	29	77
Other | Level 1
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Other | Level 2
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Other | Level 3
Defined Benefit Plan Disclosure [Line Items]
Plan assets	0	0
Other | Net Asset Value
Defined Benefit Plan Disclosure [Line Items]
Plan assets	29	77
Net receivable
Defined Benefit Plan Disclosure [Line Items]
Plan assets	$ 7
Defined Benefit Plan, Net Payable
Defined Benefit Plan Disclosure [Line Items]
Plan assets		$ (4)

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

Amount of asset segregated and restricted to provide benefit under defined benefit plan. Asset includes, but is not limited to, stock, bond, other investment, earning from investment, and contribution by employer and employee.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 2: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(01)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 4: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 55
-Paragraph 17
-URI https://asc.fasb.org/extlink&oid=123450688&loc=d3e4179-114921

Reference 5: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(iv)(02)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 6: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

Reference 7: http://www.xbrl.org/2003/role/exampleRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 1
-Subparagraph (d)(ii)
-URI https://asc.fasb.org/extlink&oid=123447040&loc=d3e1928-114920

+ Details

Name:	us-gaap_DefinedBenefitPlanFairValueOfPlanAssets
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

X

- Details

Name:	us-gaap_RetirementPlanTypeAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=arnc_DefinedBenefitPlanAssetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel1Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel2Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueInputsLevel3Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_FairValueByFairValueHierarchyLevelAxis=us-gaap_FairValueMeasuredAtNetAssetValuePerShareMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=arnc_DefinedBenefitPlanEquitiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanEquitySecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_HedgeFundsEquityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_PrivateEquityFundsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_FixedIncomeSecuritiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=arnc_FixedIncomeSecuritiesIntermediateAndLongDurationGovernmentCreditMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=arnc_FixedIncomeSecuritiesOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_OtherInvestmentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_DefinedBenefitPlanRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=us-gaap_HedgeFundsGlobalOpportunityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=arnc_DefinedBenefitPlanOtherInvestmentsExcludingRealEstateMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=arnc_DefinedBenefitPlanNetReceivableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

X

- Details

Name:	us-gaap_DefinedBenefitPlanByPlanAssetCategoriesAxis=arnc_DefinedBenefitPlanNetPayableMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: