Business combination, number of operating companies in transaction.

No definition available.

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- Definition

Notice provided to administrate agent of credit facility to draw amount.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Notice provided to administrate agent of credit facility to repay outstanding amount.

+ References

No definition available.

+ Details

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- Definition

Amount of amortization expense attributable to debt issuance costs.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
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Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03(8))
-URI http://asc.fasb.org/extlink&oid=120395209&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 3
-URI http://asc.fasb.org/extlink&oid=119993939&loc=d3e28555-108399

+ Details

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Balance Type:	debit
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the debt agreement requires the first payment to be made, in CCYY-MM-DD format.

+ References

+ Details

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

- Definition

The reference rate for the variable rate of the debt instrument, such as LIBOR or the US Treasury rate and the maturity of the reference rate used, such as three months or six months LIBOR.

+ References

No definition available.

+ Details

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

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
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-Section 45
-Paragraph 2
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-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=114775985&loc=d3e28878-108400

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

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

+ References

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
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
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Period Type:	duration

- Definition

Date when the debt instrument is scheduled to be fully repaid, in CCYY-MM-DD format.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(2))
-URI http://asc.fasb.org/extlink&oid=120391452&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 820
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (bbb)(2)
-URI http://asc.fasb.org/extlink&oid=117815213&loc=d3e19207-110258

+ Details

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

- Definition

Description of the maturity date of the debt instrument including whether the debt matures serially and, if so, a brief description of the serial maturities.

+ References

+ Details

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Period Type:	duration

- Definition

Description of the payment terms of the debt instrument (for example, whether periodic payments include principal and frequency of payments) and discussion about any contingencies associated with the payment.

+ References

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
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- Definition

Description of debt redemption features under terms of the debt agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 470
-Section 50
-Paragraph 3
-Subparagraph e
-URI http://asc.fasb.org/extlink&oid=75038535&loc=d3e64711-112823

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- Definition

Start date of debt instrument redemption period, in CCYY-MM-DD format.

+ References

+ Details

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

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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

- Definition

Present value of lessee's discounted obligation for lease payments from finance lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 50
-Paragraph 6
-URI http://asc.fasb.org/extlink&oid=121609121&loc=SL77918701-209980

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 20
-Section 45
-Paragraph 1
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=121603541&loc=SL77918627-209977

+ Details

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

- Definition

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

+ References

No definition available.

+ Details

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

- 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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-Name Accounting Standards Codification
-Topic 942
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-Section S99
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-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=120400017&loc=d3e572229-122910

+ Details

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

- Definition

Description of the fees for amounts available, but unused under the credit facility.

+ References

+ Details

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

- Definition

The effective interest rate during the reporting period.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
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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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 fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

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- Details

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- Details

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- Details

Name:	us-gaap_BusinessAcquisitionAxis=aimc_AutomationAndSpecialtyPlatformExcludingFortivesHengstlerAndDynaparBusinessesMember
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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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Debt - Additional Information (Detail)		6 Months Ended
Debt - Additional Information (Detail)	Oct. 01, 2018 USD ($) Company	Jun. 30, 2020 USD ($)	Jun. 30, 2019 USD ($)	May 27, 2020 USD ($)	Apr. 27, 2020 USD ($)	Apr. 14, 2020 USD ($)	Mar. 16, 2020 USD ($)	Mar. 09, 2020 USD ($)	Dec. 31, 2019 USD ($)
Debt Instrument [Line Items]
Amortization of deferred financing costs		$ 2,300,000	$ 2,300,000
Finance lease obligations		$ 300,000							$ 500,000
Mortgages and Other Agreements [Member]
Debt Instrument [Line Items]
Description about maturity date of debt instrument		The debt has interest rates that range from 1.79% to 2.5%, with various quarterly and monthly installments through 2028.
Minimum [Member] \| Mortgages and Other Agreements [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate percentage		1.79%
Maximum [Member] \| Mortgages and Other Agreements [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate percentage		2.50%
A&S Business [Member]
Debt Instrument [Line Items]
Business combination, number of operating companies in transaction \| Company	4
6.125% Senior Notes Due 2026 [Member] \| Newco [Member] \| A&S Business [Member]
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount	$ 400,000,000
Debt instrument, interest rate percentage	6.125%
Debt instrument, maturity date	Oct. 01, 2026
Debt instrument, interest payment terms		Interest on the Notes accrues from October 1, 2018, and the first interest payment date on the Notes was on April 1, 2019. The Notes may be redeemed at the option of the issuer on or after October 1, 2023.
Debt instrument, first interest payment date	Apr. 01, 2019
Debt instrument, redemption, description		The Notes may be redeemed at the option of the issuer on or after October 1, 2023
Debt instrument, redemption period, start date	Oct. 01, 2023
Altra Credit Agreement [Member]
Debt Instrument [Line Items]
Amortization of deferred financing costs		$ 29,900,000
Notice provided to administrate agent of credit facility to draw amount							$ 50,000,000	$ 50,000,000
Notice provided to administrate agent of credit facility to repay outstanding amount				$ 35,000,000	$ 15,000,000	$ 50,000,000
Outstanding debt		1,160,000,000.0
Letters of credit outstanding		$ 5,200,000							$ 4,400,000
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member]
Debt Instrument [Line Items]
Debt instrument, term	7 years
Maximum amount available	$ 1,340,000,000.0
Debt instrument, description of variable rate basis		Borrowings under the Altra Term Loan Facility will bear interest at a per annum rate equal to a “Eurocurrency Rate” plus 2.00%, in the case of Eurocurrency Rate borrowings, or equal to a “Base Rate” plus 1.00%, in the case of Base Rate borrowings.
Credit facility, commitment fee description		the Company will be required to pay fees that will fluctuate between 0.250% per annum to 0.375% per annum on the unused amount of the Altra Revolving Credit Facility, based upon the Company’s senior secured net leverage ratio
Line of credit facility, interest rate during period		2.174%
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member] \| Eurocurrency Rate [Member]
Debt Instrument [Line Items]
Applicable margins for loans	2.00%
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member] \| Base Rate [Member]
Debt Instrument [Line Items]
Applicable margins for loans	1.00%
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member] \| Minimum [Member]
Debt Instrument [Line Items]
Credit facility, unused capacity, commitment fee percentage	0.25%
Altra Credit Agreement [Member] \| Altra Term Loan Facility [Member] \| Maximum [Member]
Debt Instrument [Line Items]
Credit facility, unused capacity, commitment fee percentage	0.375%
Altra Credit Agreement [Member] \| Altra Revolving Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument, term	5 years
Maximum amount available	$ 300,000,000.0
Debt instrument, description of variable rate basis		Borrowings under the Altra Revolving Credit Facility will initially bear interest at a per annum rate equal to a Eurocurrency Rate plus 2.00%, in the case of Eurocurrency Rate borrowings, or equal to a Base Rate plus 1.00%, in the case of Base Rate borrowings
Amount available under credit facility		$ 294,800,000
Altra Credit Agreement [Member] \| Altra Revolving Credit Facility [Member] \| Eurocurrency Rate [Member]
Debt Instrument [Line Items]
Applicable margins for loans	2.00%
Altra Credit Agreement [Member] \| Altra Revolving Credit Facility [Member] \| Base Rate [Member]
Debt Instrument [Line Items]
Applicable margins for loans	1.00%