Restructuring, Asset Impairment, and Transition Expenses - Additional Information (Detail) - USD ($)	3 Months Ended		9 Months Ended
	Sep. 30, 2018	Sep. 30, 2017	Sep. 30, 2018	Sep. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 610,000	$ 680,000	$ 2,119,000	$ 3,776,000
2015 Altra Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	49,000		3,145,000
2017 Altra Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	610,000	$ 631,000	2,119,000	$ 631,000
2017 Altra Plan [Member] | Minimum [Member]
Restructuring Cost and Reserve [Line Items]
Expected additional restructuring cost remaining	1,000,000		1,000,000
2017 Altra Plan [Member] | Maximum [Member]
Restructuring Cost and Reserve [Line Items]
Expected additional restructuring cost remaining	$ 3,000,000		$ 3,000,000