Restructuring, Asset Impairment, and Transition Expenses - Additional Information (Detail) - USD ($) $ in Millions	3 Months Ended						9 Months Ended
	Sep. 30, 2019	Jun. 30, 2019	Mar. 31, 2019	Sep. 30, 2018	Jun. 30, 2018	Mar. 31, 2018	Sep. 30, 2019	Sep. 30, 2018
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 6.2	$ 3.2	$ 2.3	$ 0.6	$ 0.6	$ 0.9	$ 11.7	$ 2.1
2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	2.3	1.8	1.0	$ 0.6	$ 0.6	$ 0.9	5.0
Expected additional restructuring cost remaining	1.0						1.0
2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	3.9	$ 1.4	$ 1.3				$ 6.7
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	20.0						$ 20.0
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	1.6						2.7
Severance [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	3.2
Consolidation costs [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs							0.4
Employee Relocation [Member] | 2017 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	0.1						0.2
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	0.6						1.7
Other Restructuring Costs [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs	$ 0.7						0.3
Workforce reductions [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs							5.4
Facilities Consolidation [Member] | 2019 Altra Plan [Member]
Restructuring Cost And Reserve [Line Items]
Restructuring costs							$ 1.0