Restructuring, Asset Impairment, and Transition Expenses - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended				6 Months Ended
	Jun. 30, 2019	Mar. 31, 2019	Jun. 30, 2018	Mar. 31, 2018	Jun. 30, 2019	Jun. 30, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 3.2	$ 2.3	$ 0.6	$ 0.9	$ 5.5	$ 1.5
2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	1.8	1.0	$ 0.6	$ 0.9	2.8
2017 Altra Plan [Member] | Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	1.0				1.0
2017 Altra Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	3.0				3.0
2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	1.4	$ 1.3			$ 2.7
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	15.0				$ 15.0
2019 Altra Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	25.0				25.0
Severance [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.7				1.2
Severance [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	1.2				2.3
Consolidation costs [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.3				0.6
Employee Relocation [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.1				0.1
Employee Relocation [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs					0.1
Other Restructuring Costs [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.7				0.9
Other Restructuring Costs [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 0.2				$ 0.3