Restructuring, Asset Impairment, and Transition Expenses - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 2.3	$ 0.9
2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	1.0	$ 0.9
2017 Altra Plan [Member] | Minimum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	1.0
2017 Altra Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	3.0
2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 1.3
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
2019 Altra Plan [Member] | Maximum [Member]
Restructuring Cost And Reserve [Line Items]
Expected additional restructuring cost remaining	25.0
Severance [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.5
Severance [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	1.1
Consolidation costs [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.3
Other Restructuring Costs [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.2
Other Restructuring Costs [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.1
Employee Relocation | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 0.1