Face (par) amount of the original debt instrument that was repurchased.

No definition available.

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

- Definition

Difference between the fair value of payments made and the carrying amount of debt which is extinguished prior to maturity.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 4
-URI https://asc.fasb.org/extlink&oid=126972273&loc=d3e12355-112629

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 50
-Section 40
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=126972273&loc=d3e12317-112629

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3602-108585

+ Details

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

- Definition

Amount of cash paid for interest, including, but not limited to, capitalized interest and payment to settle zero-coupon bond attributable to accreted interest of debt discount and debt instrument with insignificant coupon interest rate in relation to effective interest rate of borrowing attributable to accreted interest of debt discount; classified as operating and investing activities.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 50
-Paragraph 2
-URI https://asc.fasb.org/extlink&oid=126999549&loc=d3e4297-108586

+ Details

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

- Definition

Amount of cash outflow for cost from early extinguishment and prepayment of debt. Includes, but is not limited to, third-party cost, premium paid, and other fee paid to lender directly for debt extinguishment or debt prepayment. Excludes accrued interest.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 15
-Subparagraph (g)
-URI https://asc.fasb.org/extlink&oid=126954810&loc=d3e3291-108585

+ Details

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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Period Type:	duration

- Details

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- Details

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- Details

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Namespace Prefix:
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Balance Type:
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- Details

Name:	us-gaap_DebtInstrumentAxis=amch_SeniorSubordinatedNotesDue2026Member
Namespace Prefix:
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SUBSEQUENT EVENTS - Debt repurchase transactions (Details) - USD ($) $ in Millions		12 Months Ended
	Feb. 07, 2023	Dec. 31, 2022	Dec. 31, 2021	Dec. 31, 2020
SUBSEQUENT EVENT
Gains (Losses) on Extinguishment of Debt		$ (92.8)	$ (14.1)	$ 93.6
Accrued interest paid		4.5
Second Lien Notes due 2026
SUBSEQUENT EVENT
Gains (Losses) on Extinguishment of Debt		$ 75.0
Subsequent Events
SUBSEQUENT EVENT
Debt Instrument, Repurchased Face Amount	$ 70.2
Reacquisition Cost	38.1
Gains (Losses) on Extinguishment of Debt	44.3
Accrued interest paid	1.0
Subsequent Events \| Related party transactions
SUBSEQUENT EVENT
Debt Instrument, Repurchased Face Amount	46.0
Reacquisition Cost	26.1
Gains (Losses) on Extinguishment of Debt	27.6
Accrued interest paid	0.8
Subsequent Events \| Non-related party transactions
SUBSEQUENT EVENT
Debt Instrument, Repurchased Face Amount	24.2
Reacquisition Cost	12.0
Gains (Losses) on Extinguishment of Debt	16.7
Accrued interest paid	0.2
Subsequent Events \| Second Lien Notes due 2026 \| Related party transactions
SUBSEQUENT EVENT
Debt Instrument, Repurchased Face Amount	41.9
Reacquisition Cost	24.4
Gains (Losses) on Extinguishment of Debt	25.3
Accrued interest paid	0.7
Subsequent Events \| Second Lien Notes due 2026 \| Non-related party transactions
SUBSEQUENT EVENT
Debt Instrument, Repurchased Face Amount	24.2
Reacquisition Cost	12.0
Gains (Losses) on Extinguishment of Debt	16.7
Accrued interest paid	0.2
Subsequent Events \| 5.875% Senior Subordinated Notes due 2026 \| Related party transactions
SUBSEQUENT EVENT
Debt Instrument, Repurchased Face Amount	4.1
Reacquisition Cost	1.7
Gains (Losses) on Extinguishment of Debt	2.3
Accrued interest paid	$ 0.1