Restructuring, Asset Impairment, and Transition Expenses - Additional Information (Detail) - USD ($)	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 4,449,000	$ 4,143,000	$ 9,849,000
2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	4,165,000	652,000
2017 Altra Plan [Member] | Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	500,000
2017 Altra Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	$ 1,000,000
2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Expected period to incur restructuring expense	4 years
2019 Altra Plan [Member] | Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	$ 15,000,000
2019 Altra Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	25,000,000
2015 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	300
Severance [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs		1,600,000	2,700,000
Severance [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	2,500,000	400,000
Consolidation costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs		1,200,000	1,700,000
Consolidation costs [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	600,000	200,000
Building impairments [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs			900,000
Moving and relocation [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs			2,800,000
Moving and relocation [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	300,000
Other restructuring costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs			$ 1,700,000
Other Restructuring Costs [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs		$ 1,300,000
Other Restructuring Costs [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 800,000