v3.22.0.1

Pension and Other Postretirement Benefits - Expenses (Details) - USD ($) $ in Millions | 12 Months Ended
--- | ---
Dec. 31, 2021 | Dec. 31, 2020 | Dec. 31, 2019
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Pension and other postretirement benefits cost | $ 87 | $ 103 | $ 111
Pension benefits​ |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Net periodic benefit cost | 68 | 82 | 5
Multiemployer contribution expense | 0 | 0 | 61
Cost allocation | 0 | (1) | 20
Pension and other postretirement benefits cost | 68 | 81 | 86
Actuarial loss attributable to change in discount rate used to determine benefit obligation | (130) | 370 |
Other postretirement benefits |  |  |
Defined Benefit Plans and Other Postretirement Benefit Plans Table Text Block [Line Items] |  |  |
Net periodic benefit cost | 19 | 22 | 0
Multiemployer contribution expense | 0 | 0 | 21
Cost allocation | 0 | 0 | 4
Pension and other postretirement benefits cost | $ 19 | $ 22 | $ 25

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- Definition Defined Benefit Plan, Assumptions Used Calculating Benefit Obligation, Actuarial Gain (Loss) Attributable To Change In Discount Rate + References No definition available. + Details
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Namespace Prefix: | arnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

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- Definition Defined Benefit Plan, Net Periodic Benefit Cost (Credit), Excluding Gain (Loss) Due To Settlement And Curtailment + References No definition available. + Details
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Namespace Prefix: | arnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Multiemployer Plan, Contribution Expenses + References No definition available. + Details
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Namespace Prefix: | arnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

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- Definition Pension and Other Postretirement Benefits Cost, Allocated Costs + References No definition available. + Details
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Namespace Prefix: | arnc_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
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- 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
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- Definition Amount of cost (reversal of cost) for pension and other postretirement benefits. + References No definition available. + Details
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Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
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- Details
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Namespace Prefix: |
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- Details
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