DEBT - Credit Facilities Outstanding (Details) $ in Thousands	Mar. 31, 2022 USD ($)
Debt Instrument [Line Items]
Supply chain financing to be paid within one year	$ 124,968
Cablevision Lightpath LLC \| Cablevision Lightpath LLC
Debt Instrument [Line Items]
Ownership percentage of noncontrolling interest	50.01%
CSC Holdings Revolving Credit Facility \| Revolving Credit Facility
Debt Instrument [Line Items]
Letters of credit outstanding	$ 133,706
Line of credit facility, remaining borrowing capacity	1,601,294
Line of Credit Facility, Maximum Borrowing Capacity	2,475,000
Cablevision Lightpath Term B Loan \| Secured Debt [Member]
Debt Instrument [Line Items]
Line of Credit Facility, Maximum Borrowing Capacity	$ 100,000

Supply chain financing to be paid within one year

No definition available.

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Namespace Prefix:	atus_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

+ Details

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

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

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

- Definition

The parent entity's interest in net assets of the subsidiary, expressed as a percentage.

+ References

No definition available.

+ Details

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

- Details

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- Details

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Namespace Prefix:
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- Details

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Namespace Prefix:
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- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
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- Details

Name:	us-gaap_DebtInstrumentAxis=atus_CablevisionLightpathTermBLoanMember
Namespace Prefix:
Data Type:	na
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- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
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