Percentage of performance target.

No definition available.

Name:	amch_PercentageOfPerformanceTarget
Namespace Prefix:	amch_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Weighted average fair value as of the grant date of equity-based award plans other than stock (unit) option plans that were not exercised or put into effect as a result of the occurrence of cancellation.

+ References

No definition available.

+ Details

Name:	amch_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsCancelledWeightedAverageGrantDateFairValue
Namespace Prefix:	amch_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of equity instruments other than options awarded for the next two fiscal years however the grant date fair values are subject to determination in that particular fiscal year under the share based compensation arrangement.

+ References

No definition available.

+ Details

Name:	amch_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedAwardedForNextTwoFiscalYearsNumber
Namespace Prefix:	amch_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Total number of equity instruments other than options outstanding including the awards for which the grant date fair values are subject to determination in that particular fiscal year under the share based compensation arrangement.

+ References

No definition available.

+ Details

Name:	amch_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedTotalNumber
Namespace Prefix:	amch_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of cash outflow to satisfy grantee's tax withholding obligation for award under share-based payment arrangement.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 230
-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

+ Details

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

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that were forfeited during the reporting period.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeituresWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of grants made during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value at grant date for nonvested equity-based awards issued during the period on other than stock (or unit) option plans (for example, phantom stock or unit plan, stock or unit appreciation rights plan, performance target plan).

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of non-vested equity-based payment instruments, excluding stock (or unit) options, that validly exist and are outstanding as of the balance sheet date.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(i)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

Reference 2: http://www.xbrl.org/2003/role/disclosureRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(ii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsNonvestedNumber
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ References

No definition available.

+ Details

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

- Definition

Per share or unit weighted-average fair value of nonvested award under share-based payment arrangement. Excludes share and unit options.

+ References

+ Details

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

- References

No definition available.

+ Details

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

- Definition

The net total number of shares (or other type of equity) under an equity-based award plan, other than a stock option plan, that were granted, vested and forfeited during the reporting period.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 718
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Subparagraph (c)(2)(iii)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480429/718-10-50-2

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The number of equity-based payment instruments, excluding stock (or unit) options, that vested during the reporting period.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriod
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

The weighted average fair value as of grant date pertaining to an equity-based award plan other than a stock (or unit) option plan for which the grantee gained the right during the reporting period, by satisfying service and performance requirements, to receive or retain shares or units, other instruments, or cash in accordance with the terms of the arrangement.

+ References

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsVestedInPeriodWeightedAverageGrantDateFairValue
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:perShareItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_AwardTypeAxis=amch_SpecialPerformanceStockUnitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=amch_CumulativeAdjustedEbitdaTargetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=amch_CumulativeAdjustedFreeCashFlowTargetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_RestrictedStockUnitsRSUMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=us-gaap_PerformanceSharesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=amch_SpecialAwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=amch_TwoThousandTwentyFivePerformanceShareAwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VestingAxis=amch_MeetingOfStrategicInitiativesTargetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_AwardTypeAxis=amch_TwoThousandTwentySixPerformanceShareAwardMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

STOCKHOLDERS' DEFICIT - RSU, PSU activity (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Weighted Average Grant Date Fair Value
Taxes paid for restricted unit withholdings	$ 4.4	$ 2.2	$ 14.2
Special Performance Stock \| Cumulative Adjusted EBITDA Target
Weighted Average Grant Date Fair Value
Percentage of performance target	0.00%
Special Performance Stock \| Cumulative Adjusted Free Cash Flow Target
Weighted Average Grant Date Fair Value
Percentage of performance target	0.00%
Restricted stock unit
Shares of RSU and PSU
Balance at the beginning of the period (in shares)	2,594,497
Granted (in shares)	3,122,126
Vested (in shares)	(479,247)
Forfeited (in shares)	(211,485)
Cancelled (in shares)	(452,813)
Nonvested at the end of the period (in shares)	4,573,078	2,594,497
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share)	$ 9.35
Granted (in dollars per share)	3.57	$ 5.15	$ 35.04
Vested (in dollars per share)	13.03
Forfeited (in dollars per share)	7.02
Cancelled (in dollars per share)	13.36
Nonvested at the end of the period (in dollars per share)	$ 4.73	$ 9.35
Total nonvested at December 31, 2025	4,573,078
Taxes paid for restricted unit withholdings	$ 4.4
Performance Vesting
Shares of RSU and PSU
Balance at the beginning of the period (in shares)	1,281,617
Granted (in shares)	324,969
Vested (in shares)	(682,193)
Cancelled (in shares)	(599,424)
Nonvested at the end of the period (in shares)	324,969	1,281,617
Weighted Average Grant Date Fair Value
Balance at the beginning of the period (in dollars per share)	$ 5.03
Granted (in dollars per share)	3.57	$ 5.03	$ 40.4
Vested (in dollars per share)	5.03
Cancelled (in dollars per share)	5.03
Nonvested at the end of the period (in dollars per share)	$ 3.57	$ 5.03
Tranche Years 2026 and 2027 awarded under the 2025 PSU award and Tranche Year 2026 awarded under the 2024 PSU award with grant date fair values to be determined in year 2026 and 2027, respectively	3,000,921
Total nonvested at December 31, 2025	3,325,890
Performance Vesting \| Special Award
Shares of RSU and PSU
Granted (in shares)	265,912
Vested (in shares)	(140,982)
Cancelled (in shares)	(124,930)
Weighted Average Grant Date Fair Value
Granted (in dollars per share)	$ 3.57
Vested (in dollars per share)	3.57
Cancelled (in dollars per share)	$ 3.57
2025 Performance share award \| Meeting of strategic initiatives target
Weighted Average Grant Date Fair Value
Percentage of performance target	200.00%
2026 Performance share award \| Meeting of strategic initiatives target
Weighted Average Grant Date Fair Value
Percentage of performance target	100.00%