Restructuring, Asset Impairment, and Transition Expenses - Summary of Total Restructuring Expense (Detail) - USD ($)	3 Months Ended		6 Months Ended
	Jun. 30, 2018	Jun. 30, 2017	Jun. 30, 2018	Jun. 30, 2017
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 566,000	$ 1,198,000	$ 1,509,000	$ 3,096,000
Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	566,000	2,413,000	1,509,000	4,316,000
2015 Altra Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	0	1,198,000		3,096,000
2015 Altra Plan [Member] | Operating Segments [Member] | Couplings, Clutches and Brakes [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		488,000		1,849,000
2015 Altra Plan [Member] | Operating Segments [Member] | Gearing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		488,000		784,000
2015 Altra Plan [Member] | Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$ 222,000		$ 463,000
2017 Altra Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	566,000		1,509,000
2017 Altra Plan [Member] | Operating Segments [Member] | Couplings, Clutches and Brakes [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	479,000		1,421,000
2017 Altra Plan [Member] | Operating Segments [Member] | Gearing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	85,000		67,000
2017 Altra Plan [Member] | Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	$ 2,000		$ 21,000