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

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 470
-SubTopic 20
-Section 50
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-Subparagraph (a)
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-Name Accounting Standards Codification
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-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ 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

+ Details

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

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 20
-Section 50
-Paragraph 1
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-Publisher FASB
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Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
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+ Details

Name:	us-gaap_InterestExpense
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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.

+ 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
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+ Details

Name:	us-gaap_LineOfCredit
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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- 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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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Details

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- Details

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- Details

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- Details

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- Details

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- Details

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Balance Type:
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- Details

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Balance Type:
Period Type:

- Details

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- Details

Name:	us-gaap_LineOfCreditFacilityAxis=altg_OriginalEquipmentManufacturerCaptiveLendersAndSuppliersMember
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Lines of Credit and Floor Plans - Additional Information (Details) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019	Jun. 30, 2020	Jun. 30, 2019	Feb. 14, 2020
Line Of Credit Facility [Line Items]
Recognized interest expense	$ 5,700,000	$ 5,000,000	$ 11,600,000	$ 9,500,000
Amended and Restated Credit Agreement \| JP Morgan Chase Bank \| Floor Plans
Line Of Credit Facility [Line Items]
Floor plan financing facility	165,100,000		165,100,000		$ 85,000,000
Amended and Restated Credit Agreement \| JP Morgan Chase Bank \| Aggregate Indebtedness
Line Of Credit Facility [Line Items]
Floor plan financing facility	225,000,000		225,000,000		220,000,000
Maximum borrowing capacity	225,000,000		225,000,000
Recognized interest expense	300,000		1,300,000
Amended and Restated Credit Agreement \| JP Morgan Chase Bank \| Revolving Line of Credit
Line Of Credit Facility [Line Items]
Floor plan financing facility	300,000,000		300,000,000		110,000,000
First Lien Lender \| Floor Plans
Line Of Credit Facility [Line Items]
Floor plan financing facility	40,000,000		40,000,000		$ 85,000,000
First Lien Lender \| JP Morgan Chase Bank \| Floor Plans
Line Of Credit Facility [Line Items]
Floor plan financing facility	29,000,000		29,000,000
Maximum borrowing capacity	$ 40,000,000		$ 40,000,000
Effective interest rate	2.90%		2.90%
First Lien Lender \| JP Morgan Chase Bank \| ABL Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility	$ 110,800,000		$ 110,800,000
Maximum borrowing capacity	$ 300,000,000		$ 300,000,000
Effective interest rate	2.00%		2.00%
First Lien Lender \| JP Morgan Chase Bank \| Floor Plans and ABL Facility
Line Of Credit Facility [Line Items]
Floor plan financing facility	$ 275,900,000		$ 275,900,000
Maximum borrowing capacity	525,000,000		525,000,000
Debt issuance costs	1,600,000		$ 1,600,000
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| Minimum
Line Of Credit Facility [Line Items]
Interest only or deferred payment period			5 months
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| Maximum
Line Of Credit Facility [Line Items]
Interest only or deferred payment period			12 months
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| Floor Plans
Line Of Credit Facility [Line Items]
Floor plan financing facility	136,100,000		$ 136,100,000
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| Floor Plans \| Minimum
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	$ 10,000,000		$ 10,000,000
Effective interest rate	3.10%		3.10%
Original Equipment Manufacturer ("OEM") Captive Lenders and Suppliers \| JP Morgan Chase Bank \| Floor Plans \| Maximum
Line Of Credit Facility [Line Items]
Maximum borrowing capacity	$ 82,000,000		$ 82,000,000
Effective interest rate	4.20%		4.20%