Consolidated Statements of Stockholders' Equity - USD ($) $ in Thousands	Total	Common Stock [Member]	Additional Paid in Capital [Member]	Retained Earnings [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Redeemable Non-Controlling Interest [Member]
Beginning balance at Dec. 31, 2013	$ 269,333	$ 27	$ 154,471	$ 133,231	$ (18,396)	$ 991
Beginning balance (in shares) at Dec. 31, 2013		26,820,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock	2,233		2,233
Stock-based compensation and vesting of restricted stock (in shares)		79,000
Net income attributable to Altra Industrial Motion Corp.	40,167			40,167
Net loss attributable to non-controlling interest	(15)					15
Dividends declared	(12,337)			(12,337)
Change in fair value of interest rate swap, net of tax	8				8
Pension liability adjustment, net of tax	(1,685)				(1,685)
Repurchases of common stock	(17,618)	$ (1)	(17,617)
Repurchases of common stock (in shares)		(545,000)
Cumulative foreign currency translation adjustment, net of tax	(21,342)				(21,342)	(123)
Ending balance at Dec. 31, 2014	258,759	$ 26	139,087	161,061	(41,415)	883
Ending balance (in shares) at Dec. 31, 2014		26,354,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock	2,822		2,822
Stock-based compensation and vesting of restricted stock (in shares)		82,000
Net income attributable to Altra Industrial Motion Corp.	35,406			35,406
Net loss attributable to non-controlling interest	63					(63)
Purchase of non-controlling interest	(187)		223		(410)	(691)
Dividends declared	(14,928)			(14,928)
Change in fair value of interest rate swap, net of tax	(283)				(283)
Pension liability adjustment, net of tax	(989)				(989)
Repurchases of common stock	(17,298)		(17,298)
Repurchases of common stock (in shares)		(663,000)
Cumulative foreign currency translation adjustment, net of tax	(20,735)				(20,735)	$ (129)
Ending balance at Dec. 31, 2015	242,567	$ 26	124,834	181,539	(63,832)
Ending balance (in shares) at Dec. 31, 2015		25,773,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock	2,893		2,893
Stock-based compensation and vesting of restricted stock (in shares)		74,000
Net income attributable to Altra Industrial Motion Corp.	25,140			25,140
Net loss attributable to non-controlling interest	0
Conversion of Convertible Debt	45,286	$ 1	45,285
Conversion of Convertible Debt (in shares)		1,536,000
Dividends declared	(15,571)			(15,571)
Change in fair value of interest rate swap, net of tax	(506)				(506)
Pension liability adjustment, net of tax	139				139
Repurchases of common stock	$ (4,713)		(4,713)
Repurchases of common stock (in shares)	(177,053)	(177,000)
Cumulative foreign currency translation adjustment, net of tax	$ (11,887)				(11,887)
Ending balance at Dec. 31, 2016	$ 283,348	$ 27	$ 168,299	$ 191,108	$ (76,086)
Ending balance (in shares) at Dec. 31, 2016		27,206,000