Line of credit facility interest only or deferred payment period.

No definition available.

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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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Data Type:	dtr-types:percentItemType
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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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

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

- Details

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Namespace Prefix:
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Balance Type:
Period Type:

- Details

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Data Type:	na
Balance Type:
Period Type:

- Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=altg_FloorPlansAndAssetBasedLendingFacilityMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=altg_OriginalEquipmentManufacturerCaptiveLendersAndSuppliersMember
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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

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Balance Type:
Period Type:

- Details

Name:	srt_RangeAxis=srt_MaximumMember
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Balance Type:
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- Details

Name:	us-gaap_CreditFacilityAxis=altg_OEMFloorPlanFacilitiesMember
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Balance Type:
Period Type:

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=altg_FourthAmendedAndRestatedFirstLienCreditAgreementMember
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Lines of Credit and Floor Plans - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021	Dec. 31, 2021	Apr. 01, 2021
Line Of Credit Facility [Line Items]
Recognized interest expense	$ 6,800,000	$ 6,000,000.0	$ 12,900,000	$ 11,800,000
First Lien Lender \| JP Morgan Chase Bank \| ABL Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility	$ 125,600,000		$ 125,600,000		$ 100,700,000
Maximum borrowing capacity						$ 350,000,000.0
Effective interest rate	3.60%		3.60%		2.30%
First Lien Lender \| JP Morgan Chase Bank \| First Lien Floor Plan Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility	$ 42,700,000		$ 42,700,000		$ 30,600,000
Maximum borrowing capacity	$ 50,000,000.0		$ 50,000,000.0
Effective interest rate	3.90%		3.90%		2.80%
First Lien Lender \| JP Morgan Chase Bank \| Floor Plans and ABL Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility	$ 324,300,000		$ 324,300,000		$ 255,600,000
Maximum borrowing capacity	700,000,000.0		700,000,000.0
Debt issuance costs	2,100,000		2,100,000		2,400,000
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| Floor Plan Facilities \| Minimum
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	100,000		100,000
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| Floor Plan Facilities \| Maximum
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	102,000,000.0		102,000,000.0
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	$ 156,000,000.0		$ 156,000,000.0		124,300,000
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| OEM Floor Plan Facilities \| Minimum
Line Of Credit Facility [Line Items]
Effective interest rate	3.80%		3.80%
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| OEM Floor Plan Facilities \| Maximum
Line Of Credit Facility [Line Items]
Effective interest rate	5.90%		5.90%
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	$ 198,700,000		$ 198,700,000		$ 154,900,000
Maximum borrowing capacity	0.0		0.0
Recognized interest expense	$ 500,000	$ 500,000	$ 800,000	$ 1,000,000.0