Aggregate cash contribution to pension plan.

No definition available.

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Namespace Prefix:	arnc_
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Period Type:	duration

- Definition

Cash contribution term to pension plan.

+ References

No definition available.

+ Details

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- Definition

Amount of gain (loss) recognized in net periodic benefit (cost) credit from event reducing expected years of future service of present employees or eliminating accrual of defined benefits for some or all future services of present employees.

+ 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 (h)(7)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e1928-114920

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 20
-Section 50
-Paragraph 6
-Subparagraph (a)(7)
-URI http://asc.fasb.org/extlink&oid=108410482&loc=d3e2709-114920

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Balance Type:	credit
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- Definition

Amount of increase (decrease) in obligation for pension benefits. Includes, but is not limited to, defined benefit or defined contribution plans. Excludes other postretirement benefits.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

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Period Type:	duration

- Definition

Amount, after tax and reclassification adjustment, of (increase) decrease in accumulated other comprehensive income for defined benefit plan.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 11
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-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section 45
-Paragraph 10A
-Subparagraph (i-k)
-URI http://asc.fasb.org/extlink&oid=114867106&loc=SL7669646-108580

+ Details

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- Definition

Amount of cash outflow for pension and other postretirement benefits. Includes, but is not limited to, employer contribution to fund plan asset and payment to retiree.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (g)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3536-108585

+ Details

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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 420
-SubTopic 10
-Section S99
-Paragraph 1
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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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- Details

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- Details

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Pension and Other Postretirement Benefits - Narrative (Details) - USD ($) $ in Millions		1 Months Ended			3 Months Ended
	Nov. 01, 2016	Apr. 30, 2019	Mar. 31, 2018	Apr. 30, 2017	Mar. 31, 2019	Mar. 31, 2018
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and other charges (benefits)					$ 12	$ 7
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits					40	143
Aggregate cash cash contribution to pension plan	$ 150
Cash contribution term to pension plan	30 months
Cash payments made for pension and other post-retirement benefits			$ 66	$ 50
Other postretirement benefits
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Curtailment benefit (charges)					58	0
Pension Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Curtailment benefit (charges)					0	(5)
UNITED STATES \| Other postretirement benefits
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in obligation, pension benefits					(63)
Curtailment benefit (charges)					(58)
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits					(5)
UNITED STATES \| Pension Plan
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in obligation, pension benefits						(136)
Curtailment benefit (charges)						5
Change in unrecognized net actuarial loss and prior service cost/benefit related to pension and other postretirement benefits						$ 141
Subsequent Event
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Cash payments made for pension and other post-retirement benefits		$ 34
Pension Settlement Cost
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Restructuring and other charges (benefits)					2
Elimination Of Health Care Subsidies \| UNITED STATES \| Other postretirement benefits
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]
Decrease in obligation, pension benefits					$ (12)