Debt - Additional Information (Detail) - USD ($)		6 Months Ended
	Oct. 01, 2018	Jun. 30, 2019	Jun. 30, 2018	Dec. 31, 2018
Debt Instrument [Line Items]
Amortization of deferred financing costs		$ 2,300,000	$ 300,000
Finance lease obligations		500,000		$ 500,000
Mortgages and Other Agreements [Member]
Debt Instrument [Line Items]
Outstanding debt		$ 2,400,000
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%
2015 Revolving credit facility [Member]
Debt Instrument [Line Items]
Maximum amount available	$ 425,000,000
Line of Credit [Member] | Mortgages and Other Agreements [Member] | China [Member]
Debt Instrument [Line Items]
Debt instrument, aggregate principal amount		$ 7,500,000
Debt instrument, term		1 year
6.125% Senior Notes Due 2026 [Member] | Newco [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 next interest payment date on the Notes will be due July 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	Jul. 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
Outstanding debt		1,270,000,000.0
Letters of credit outstanding		$ 4,400,000		$ 4,200,000
Altra Credit Agreement [Member] | Minimum [Member]
Debt Instrument [Line Items]
Credit facility, unused capacity, commitment fee percentage	0.25%
Altra Credit Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Credit facility, unused capacity, commitment fee percentage	0.375%
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.
Line of credit facility, interest rate during period		4.40%
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 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
Line of credit facility, interest rate during period		4.40%
Amount available under credit facility		$ 295,600,000
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%