Consolidated Statements of Comprehensive Income - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2017	Dec. 31, 2016	Dec. 31, 2015
Statement Of Income And Comprehensive Income [Abstract]
Net income	$ 51,427	$ 25,140	$ 35,343
Other comprehensive income (loss):
Reclassification adjustment from loss on partial settlement of pension plan, net of tax	1,066	0	0
Pension liability adjustment, net of tax	924	139	(989)
Change in fair value of interest rate swap, net of tax	194	(506)	(283)
Foreign currency translation adjustment, net of tax	24,038	(11,887)	(20,735)
Total comprehensive income	77,649	12,886	13,336
Comprehensive income attributable to non-controlling interest	0	0	(129)
Comprehensive income attributable to Altra Industrial Motion Corp.	$ 77,649	$ 12,886	$ 13,207