Restructuring, Asset Impairment, and Transition Expenses - Summary of Total Restructuring Expense (Detail) - USD ($) $ in Thousands		12 Months Ended
		Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$ 4,143	$ 9,849	$ 7,214
Operating Segments [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		4,143	9,849	7,214
2015 Altra Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		3,491	9,849	7,214
2015 Altra Plan [Member] | Operating Segments [Member] | Couplings, Clutches and Brakes [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		1,849	7,302	2,527
2015 Altra Plan [Member] | Operating Segments [Member] | Electromagnetic Clutches and Brakes [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		50	1,286	1,600
2015 Altra Plan [Member] | Operating Segments [Member] | Gearing [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		1,076	287	3,080
2015 Altra Plan [Member] | Corporate [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs	[1]	516	$ 974	$ 7
2017 Altra Plan [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		652
2017 Altra Plan [Member] | Operating Segments [Member] | Couplings, Clutches and Brakes [Member]
Restructuring Cost and Reserve [Line Items]
Restructuring costs		$ 652

[1] Certain expenses are maintained at the corporate level and not allocated to the segments. These include various administrative expenses related to corporate headquarters, depreciation on capitalized software costs, non-capitalizable software implementation costs and acquisition related expenses and non-cash partial pension settlements.