Credit line borrowings of instance amounts borrowed on OEM floor plan facilities.

No definition available.

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

- Definition

Line of credit facility interest only or deferred payment period.

+ References

No definition available.

+ Details

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Namespace Prefix:	altg_
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Balance Type:	na
Period Type:	duration

- Definition

Vendor floor plan limits.

+ References

No definition available.

+ Details

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Namespace Prefix:	altg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

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+ Details

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Balance Type:	na
Period Type:	instant

- Definition

Amount, after accumulated amortization, of debt issuance costs. Includes, but is not limited to, legal, accounting, underwriting, printing, and registration costs.

+ References

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

- Definition

Amount of the cost of borrowed funds accounted for as interest expense.

+ References

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+ Details

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

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

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+ Details

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Namespace Prefix:	us-gaap_
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

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- 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

+ Details

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Balance Type:	credit
Period Type:	instant

- Details

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Balance Type:
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- Details

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Balance Type:
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- Details

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- Details

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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=altg_ABLFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=altg_FirstLienLenderMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=altg_FirstLienFloorPlanFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_CreditFacilityAxis=altg_FloorPlansAndAssetBasedLendingFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Period Type:

- Details

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Lines of Credit and Floor Plans - Additional Information (Details) - USD ($)			12 Months Ended
	Dec. 20, 2021	Jan. 11, 2021	Dec. 31, 2021	Dec. 31, 2020	Apr. 01, 2021
Line Of Credit Facility [Line Items]
Recognized interest expense			$ 24,000,000.0	$ 23,800,000
Restated A B L First Lien Credit Agreement
Line Of Credit Facility [Line Items]
Credit line borrowings of instance amounts borrowed on OEM floor plan facilities		$ 225,000,000
Restated A B L First Lien Credit Agreement \| Minimum
Line Of Credit Facility [Line Items]
Vendor floor plan limits		225,000,000
Restated A B L First Lien Credit Agreement \| Maximum
Line Of Credit Facility [Line Items]
Vendor floor plan limits		$ 250,000,000
Sixth Amended and Restated ABL First Lien Credit Agreement \| JP Morgan Chase Bank
Line Of Credit Facility [Line Items]
Vendor floor plan limits	$ 350,000,000
Sixth Amended and Restated ABL First Lien Credit Agreement \| Minimum \| JP Morgan Chase Bank \| ABL Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility					$ 300,000,000
Sixth Amended and Restated ABL First Lien Credit Agreement \| Maximum \| JP Morgan Chase Bank \| ABL Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility					$ 350,000,000
First Lien Lender \| JP Morgan Chase Bank \| ABL Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility			100,700,000	$ 159,100,000
Maximum borrowing capacity			$ 350,000,000
Effective interest rate			2.30%	2.00%
First Lien Lender \| JP Morgan Chase Bank \| First Lien Floor Plan Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility			$ 30,600,000	$ 35,300,000
Maximum borrowing capacity			$ 50,000,000
Effective interest rate			2.80%	2.90%
First Lien Lender \| JP Morgan Chase Bank \| Floor Plans and ABL Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility			$ 255,600,000	$ 316,600,000
Maximum borrowing capacity			750,000,000.0
Debt issuance costs			2,400,000	1,500,000
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| OEM Floor Plan Facilities
Line Of Credit Facility [Line Items]
Floor plan financing facility			124,300,000	122,200,000
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| Minimum \| JP Morgan Chase Bank \| Floor Plan Facilities
Line Of Credit Facility [Line Items]
Maximum borrowing capacity			$ 2,000,000
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| Minimum \| JP Morgan Chase Bank \| OEM Floor Plan Facilities
Line Of Credit Facility [Line Items]
Effective interest rate			3.10%
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| Maximum \| JP Morgan Chase Bank \| Floor Plan Facilities
Line Of Credit Facility [Line Items]
Maximum borrowing capacity			$ 102,000,000
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| Maximum \| JP Morgan Chase Bank \| OEM Floor Plan Facilities
Line Of Credit Facility [Line Items]
Effective interest rate			6.00%
Interest only or deferred payment period			12 months
Alta Enterprises, LLC, NITCO, LLC and Other Credit Parties [Member] \| JP Morgan Chase Bank \| Floor Plan Facilities
Line Of Credit Facility [Line Items]
Floor plan financing facility			$ 154,900,000	157,500,000
Maximum borrowing capacity			400,000,000.0
Recognized interest expense			$ 1,700,000	$ 2,300,000