Restructuring, Asset Impairment, and Transition Expenses - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2020	Mar. 31, 2020	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2020	Jun. 30, 2019
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 1.5	$ 1.6	$ 3.2	$ 2.3	$ 3.1	$ 5.5
2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.3	0.2	1.8	1.0	0.5	2.8
2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	1.2	$ 1.4	$ 1.4	$ 1.3	$ 2.6	$ 2.7
Expected period to incur restructuring expense					3 years
2019 Altra Plan [Member] | Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	10.0				$ 10.0
2019 Altra Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	15.0				15.0
Employee Severance, Consolidation and Other Restructuring Costs [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.3				0.5
Severance [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	1.2				1.2
Consolidation costs [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 2.6				$ 2.6