The maximum outstanding amount of accounts receivable sold.

No definition available.

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

- Definition

The amount of accounts receivable sold under the amended program.

+ References

No definition available.

+ Details

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

- Definition

The amount of accounts receivable sold under the program.

+ References

No definition available.

+ Details

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

- Definition

The amount of accounts receivable sold under the program related to continuing operations.

+ References

No definition available.

+ Details

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

- Definition

Amount of excess principal amount of debt exchanged over the principal amount of replacement debt issued in a debt modification transaction. The amount is deferred and amortized through interest expense over the remaining life of the modified debt.

+ References

No definition available.

+ Details

Name:	ach_DebtModificationPrincipalRecaptureLiability
Namespace Prefix:	ach_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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

The amount of earned and unbilled receivables as of balance sheet date.

+ References

No definition available.

+ Details

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

- Definition

Amount of cash outflow for transaction breakage fee incurred at the time of termination of merger or acquisition agreement during the reporting period.

+ References

No definition available.

+ Details

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

- 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

Proceeds from collection of accounts receivable related to continuing operations.

+ References

No definition available.

+ Details

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

- Definition

Proceeds from collection of accounts receivable under amended program.

+ References

No definition available.

+ Details

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

- Definition

Summary Of Significant Accounting Policies [Line Items]

+ References

No definition available.

+ Details

Name:	ach_SummaryOfSignificantAccountingPoliciesLineItems
Namespace Prefix:	ach_
Data Type:	xbrli:stringItemType
Balance Type:	na
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

This element represents acquisition-related costs incurred to effect a business combination which costs have been expensed during the period. Such costs include finder's fees; advisory, legal, accounting, valuation, and other professional or consulting fees; general administrative costs, including the costs of maintaining an internal acquisitions department; and may include costs of registering and issuing debt and equity securities.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 805
-SubTopic 10
-Section 25
-Paragraph 23
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147479405/805-10-25-23

+ Details

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

- Definition

Amount of actuarial present value of benefits attributed to service rendered by employee for defined benefit plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 715
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480506/715-20-50-1

+ Details

Name:	us-gaap_DefinedBenefitPlanBenefitObligation
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

+ References

No definition available.

+ Details

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

- 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

- Details

Name:	us-gaap_StatementOperatingActivitiesSegmentAxis=us-gaap_SegmentContinuingOperationsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

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

- Details

Name:	us-gaap_BusinessAcquisitionAxis=ach_RotechHealthcareHoldingsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Summary of Significant Accounting Policies - Additional Information (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2026	Jun. 30, 2025	Jun. 30, 2026	Jun. 30, 2025	Dec. 31, 2025	Oct. 07, 2025	Oct. 18, 2024
Summary Of Significant Accounting Policies
Earned and unbilled receivables	$ 33.0		$ 33.0		$ 30.0
Maximum outstanding amount of accounts receivable					150.0		$ 450.0
Net cash proceeds under the Receivables Sale program		$ 496.0		$ 840.0
Accounts receivable sold under program, continuing operations		99.0		168.0
Cash proceeds from collection of accounts receivable		495.0		704.0
Proceeds from collection of accounts receivables, continuing operations		99.0		141.0
Losses on sale of accounts receivable	1.8	(3.1)	3.3	(5.2)
Accounts receivable sold under amended program	221.0		466.0
Proceeds from accounts receivable	239.0		470.0
Uncollected accounts receivable	130.0		130.0		134.0
Accumulated benefit obligation	30.0		30.0		31.0
Acquisition-related charges	0.0	6.4	0.0	22.0
Debt modification, principal recapture liability	$ 115.0		$ 115.0
Continuing operations
Summary Of Significant Accounting Policies
Losses on sale of accounts receivable		0.6		1.1
Products & Healthcare Services
Summary Of Significant Accounting Policies
Net cash proceeds under the Receivables Sale program		397.0		672.0
Cash proceeds from collection of accounts receivable		396.0		563.0
Losses on sale of accounts receivable		(2.5)		(4.1)
Uncollected accounts receivable					$ 0.0
Products & Healthcare Services \| Discontinued Operations, Held-for-sale
Summary Of Significant Accounting Policies
Cash consideration						$ 375.0
Percentage of equity interest retained						5.00%
Rotech Healthcare Holdings Inc
Summary Of Significant Accounting Policies
Cash payment		$ 80.0		$ 80.0