The amount of accounts receivable sold under the program.

No definition available.

Name:	ach_AccountsReceivableSoldUnderProgram
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Percentage of costs agreed to reimburse the purchaser and its affiliates in connection with separation of business.

+ References

No definition available.

+ Details

Name:	ach_DisposalGroupIncludingDiscontinuedOperationCostsAgreedToReimbursePercent
Namespace Prefix:	ach_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of estimated purchase price adjustment receivable on disposal of disposal group including discontinued operations.

+ References

No definition available.

+ Details

Name:	ach_DisposalGroupIncludingDiscontinuedOperationEstimatedPurchasePriceAdjustmentReceivable
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Maximum aggregate amount the Company is obligated to reimburse the Purchaser and its affiliates for eligible separation-related costs.

+ References

No definition available.

+ Details

Name:	ach_DisposalGroupIncludingDiscontinuedOperationMaximumCostsAgreedToReimburseAmount
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of maximum credit support obliged to provide for separated business.

+ References

No definition available.

+ Details

Name:	ach_DisposalGroupIncludingDiscontinuedOperationMaximumCreditSupportAmount
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The amount of net fees for services received and for services provided in connection with separation of business.

+ References

No definition available.

+ Details

Name:	ach_DisposalGroupIncludingDiscontinuedOperationNetFeesForServicesReceivedAndForServicesProvided
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The amount of separation costs to be reimbursed in connection with separation of business.

+ References

No definition available.

+ Details

Name:	ach_DisposalGroupIncludingDiscontinuedOperationSeparationCostsToBeReimbursed
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the period of completion of service agreement.

+ References

No definition available.

+ Details

Name:	ach_DisposalGroupIncludingDiscontinuedOperationServiceAgreementPeriod
Namespace Prefix:	ach_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of equity interest the entity will retain post disposal of segment that were classified as discontinued operations.

+ References

No definition available.

+ Details

Name:	ach_DisposalGroupIncludingDiscontinuedOperationsEquityInterestRetainedAmount
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Percentage of equity interest the entity will retain post disposal of segment that were classified as discontinued operations.

+ References

No definition available.

+ Details

Name:	ach_DisposalGroupIncludingDiscontinuedOperationsPercentageOfEquityInterestRetained
Namespace Prefix:	ach_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Proceeds from collection of accounts receivable.

+ References

No definition available.

+ Details

Name:	ach_ProceedsFromCollectionOfAccountsReceivables
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of uncollected accounts receivables sold or removed as of date.

+ References

No definition available.

+ Details

Name:	ach_UncollectedAccountsReceivablesSoldOrRemoved
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Reduction in cash due to no longer including the former subsidiary's cash in the consolidated entity's cash.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 13
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-13

+ Details

Name:	us-gaap_CashDivestedFromDeconsolidation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Amount of gain (loss) on sale of accounts receivable.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 860
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 5
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481326/860-20-50-5

+ Details

Name:	us-gaap_GainLossOnSaleOfAccountsReceivable
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- 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_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The cash inflow associated with the amount received from the sale of a portion of the company's business, for example a segment, division, branch or other business, during the period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-12

+ Details

Name:	us-gaap_ProceedsFromDivestitureOfBusinesses
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

This element represents the cash inflow during the period from the sale of a component of the entity.

+ References

+ Details

Name:	us-gaap_ProceedsFromDivestitureOfBusinessesNetOfCashDivested
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=ach_ProductsHealthcareServicesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementLocationAxis=ach_GainLossOnDiscontinuedOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DisposalGroupClassificationAxis=us-gaap_DiscontinuedOperationsDisposedOfBySaleMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MinimumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=ach_ScenarioCostsIncurredPriorToOctober12026Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_StatementScenarioAxis=ach_ScenarioCostsIncurredPriorToJanuary12027Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Discontinued Operations and Assets Held-for-Sale - Narratives (Details) - USD ($)		3 Months Ended
	Dec. 31, 2025	Mar. 31, 2026	Mar. 31, 2025
Discontinued Operations
Net cash proceeds under the Receivables Sale program			$ 343,000,000
Cash proceeds from collection of accounts receivable			209,000,000
Losses on sale of accounts receivable			(400,000)
Uncollected accounts receivable	$ 134,000,000	$ 148,000,000
Products & Healthcare Services
Discontinued Operations
Net cash proceeds under the Receivables Sale program			274,000,000
Cash proceeds from collection of accounts receivable			167,000,000
Uncollected accounts receivable	0
Products & Healthcare Services \| Gain (loss) on discontinued operations
Discontinued Operations
Losses on sale of accounts receivable			$ 1,700,000
Products & Healthcare Services \| Discontinued Operations, Disposed of by Sale
Discontinued Operations
Disposal group, including discontinued operations, equity interest retained, amount	$ 20,000,000
Percentage of equity interest retained	5.00%
Proceeds from P&HS sale	$ 324,000,000
Cash proceeds received from P&HS sale	342,000,000
Cash conveyed from P&HS sale	18,000,000
Separation costs to be reimbursed		$ 18,000,000
Disposal group, including discontinued operation, costs agreed to reimburse, percent		80.00%
Disposal group, including discontinued operation, maximum costs agreed to reimburse, amount		$ 65,000,000
Disposal group, including discontinued operation, maximum credit support, amount		$ 115,000,000
Service agreement period (in years)		2 years
Net fees for services received and for services provided		$ 8,700,000
Products & Healthcare Services \| Discontinued Operations, Disposed of by Sale \| Minimum
Discontinued Operations
Disposal group, Including discontinued operation, estimated purchase price	12,000,000
Products & Healthcare Services \| Discontinued Operations, Disposed of by Sale \| Maximum
Discontinued Operations
Disposal group, Including discontinued operation, estimated purchase price	$ 15,000,000
Products & Healthcare Services \| Discontinued Operations, Disposed of by Sale \| Scenario, costs incurred prior to October 1 2026
Discontinued Operations
Disposal group, including discontinued operation, maximum costs agreed to reimburse, amount		15,000,000
Products & Healthcare Services \| Discontinued Operations, Disposed of by Sale \| Scenario, costs incurred prior to January 1 2027
Discontinued Operations
Disposal group, including discontinued operation, maximum costs agreed to reimburse, amount		$ 55,000,000