Restructuring, Asset Impairment, and Transition Expenses - Reconciliation of Accrued Restructuring Costs (Detail) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2020	Mar. 31, 2019
Restructuring Reserve [Roll Forward]
Beginning Balance	$ 4.1	$ 2.0
Restructuring expense incurred	1.6	2.3
Cash payments	(1.8)	(2.0)
Ending Balance	3.9	2.3
2017 Altra Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	1.5	2.0
Restructuring expense incurred	0.2	1.0
Cash payments	(0.4)	(1.5)
Ending Balance	1.3	1.5
2019 Altra Plan [Member]
Restructuring Reserve [Roll Forward]
Beginning Balance	2.6
Restructuring expense incurred	1.4	1.3
Cash payments	(1.4)	(0.5)
Ending Balance	$ 2.6	$ 0.8