Commitments and contingencies line items

No definition available.

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Namespace Prefix:	amch_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of excess insurance deductible.

+ References

No definition available.

+ Details

Name:	amch_ExcessInsuranceAmountDeductible
Namespace Prefix:	amch_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

The number of insurers against which lawsuit was filed.

+ References

No definition available.

+ Details

Name:	amch_LawsuitFiledAgainstInsurersNumber
Namespace Prefix:	amch_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

The amount of excess insurance paid by the primary insurer.

+ References

No definition available.

+ Details

Name:	amch_PrimaryInsurerExcessInsuranceAmountPaid
Namespace Prefix:	amch_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

The per share amount of a dividend declared, but not paid, as of the financial reporting date.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 3
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482913/230-10-50-3

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount due in settlement of a claim for reimbursement from an insurance company when the Company has suffered a loss covered under an insurance policy.

+ References

No definition available.

+ Details

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

- Definition

Amount awarded to other party in judgment or settlement of litigation.

+ References

No definition available.

+ Details

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

- Definition

Amount of litigation expense, including but not limited to legal, forensic, accounting, and investigative fees.

+ References

No definition available.

+ Details

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

- Definition

Amount of loss contingency liability.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483076/450-20-50-1

Reference 2: http://www.xbrl.org/2003/role/recommendedDisclosureRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 10
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483076/450-20-50-10

+ Details

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

- Definition

Amount charged against operating income increasing loss contingency liability, after adjustments to reduce previously estimated charges.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483076/450-20-50-1

+ Details

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

- Definition

The total number of new claims filed pertaining to a loss contingency during the period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
-SubTopic 20
-Name Accounting Standards Codification
-Section 50
-Paragraph 4
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483076/450-20-50-4

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 450
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-Section 50
-Paragraph 9
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-Publisher FASB
-URI https://asc.fasb.org//1943274/2147483076/450-20-50-9

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

- Definition

Number of pending claims pertaining to a loss contingency.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Cash received for the settlement of litigation during the current period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 25
-Subparagraph (c)
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147482740/230-10-45-25

+ Details

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Balance Type:	debit
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- Definition

Ratio applied to the conversion of stock split, for example but not limited to, one share converted to two or two shares converted to one.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 4
-Subparagraph (SAB TOPIC 4.C)
-SubTopic 10
-Topic 505
-Publisher FASB
-URI https://asc.fasb.org//1943274/2147480008/505-10-S99-4

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Period Type:	duration

- Details

Name:	srt_LitigationCaseAxis=amch_ShareholderLitigationMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

COMMITMENTS AND CONTINGENCIES (Details) $ / shares in Units, $ in Millions											3 Months Ended	9 Months Ended
	Aug. 24, 2023	Aug. 11, 2023	Jun. 14, 2023 USD ($)	May 04, 2023 USD ($) item	Apr. 02, 2023	Feb. 20, 2023 item	Jan. 06, 2023 USD ($)	Nov. 30, 2022 USD ($)	Jun. 06, 2022 USD ($)	Sep. 02, 2021 USD ($)	Sep. 30, 2023 USD ($) item	Sep. 30, 2023 USD ($) item	Sep. 14, 2018 $ / shares	Jan. 19, 2018 item	Jan. 12, 2018 item
Commitments and contingencies line items
Number of actions \| item						2
Number of pending actions \| item											2	2		2	2
Litigation settlement amount			$ 1.0							$ 18.0
Amount received from legal settlement							$ 14.0		$ 17.4
Fee and expense award to Plaintiff's counsel								$ 3.4				$ 99.3
Dividends declared \| $ / shares													$ 1.55
Stock split conversion ratio	0.1
Shareholder litigation											$ (16.1)	99.3
Number of insurers against whom lawsuit filed \| item				17
Excess amount deductible				$ 10.0
Excess amount paid by the primary insurer				$ 5.0
Shareholder Litigation
Commitments and contingencies line items
Stock split conversion ratio		0.1333			0.1333
Shareholder litigation												110.1
Litigation contingency reserve charge											99.3	99.3
Insurance Settlements Receivable											$ 10.8	$ 10.8