Consolidated Statements of Stockholders' Equity - USD ($) shares in Thousands, $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Loss [Member]	Redeemable Non-Controlling Interest [Member]
Beginning balance at Dec. 31, 2014	$ 258,759	$ 26	$ 139,087	$ 161,061	$ (41,415)	$ 883
Beginning balance (in shares) at Dec. 31, 2014		26,354
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock	2,049		2,049
Stock-based compensation and vesting of restricted stock (in shares)		76
Net income attributable to Altra Industrial Motion Corp.	29,299			29,299
Net loss attributable to non-controlling interest	63					(63)
Purchase of Minority Interest	(187)		223		(410)	(691)
Dividends declared	(11,038)			(11,038)
Change in fair value of interest rate swap	(283)				(283)
Cumulative foreign currency translation adjustment	(16,242)				(16,242)	$ (129)
Repurchases of common stock	(14,285)		(14,285)
Repurchases of common stock (in shares)		(548)
Ending balance at Sep. 30, 2015	248,072	$ 26	127,074	179,322	(58,350)
Ending balance (in shares) at Sep. 30, 2015		25,882
Beginning balance at Dec. 31, 2015	242,567	$ 26	124,834	181,539	(63,832)
Beginning balance (in shares) at Dec. 31, 2015		25,773
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock	2,082		2,082
Stock-based compensation and vesting of restricted stock (in shares)		89
Net income attributable to Altra Industrial Motion Corp.	23,472			23,472
Net loss attributable to non-controlling interest	0
Dividends declared	(11,667)			(11,667)
Cumulative foreign currency translation adjustment	(866)				(866)
Repurchases of common stock	(4,713)		(4,713)
Repurchases of common stock (in shares)		(177)
Ending balance at Sep. 30, 2016	$ 250,875	$ 26	$ 122,203	$ 193,344	$ (64,698)
Ending balance (in shares) at Sep. 30, 2016		25,685