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, 2014	$ 258,759	$ 26	$ 139,087	$ 161,061	$ (41,415)	$ 883
Beginning 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	2,087		2,087
Stock-based compensation and vesting of restricted stock (in shares)		15,000
Net income attributable to Altra Industrial Motion Corp.	19,078			19,078
Net loss attributable to non-controlling interest	63					(63)
Purchase of Minority Interest	(187)		223		(410)	(691)
Dividends declared	(7,129)			(7,129)
Change in fair value of interest rate swap	(219)				(219)
Cumulative foreign currency translation adjustment	(11,768)				(11,768)	(129)
Repurchases of common stock	(8,006)		(8,006)
Repurchases of common stock (in shares)		(294,000)
Ending balance at Jun. 30, 2015	252,615	$ 26	133,391	173,010	(53,812)	0
Ending balance (in shares) at Jun. 30, 2015		26,075,000
Beginning balance at Dec. 31, 2015	242,567	$ 26	124,834	181,539	(63,832)	0
Beginning 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	2,208		2,208
Stock-based compensation and vesting of restricted stock (in shares)		19,000
Net income attributable to Altra Industrial Motion Corp.	18,159			18,159
Net loss attributable to non-controlling interest	0
Dividends declared	(7,791)			(7,791)
Cumulative foreign currency translation adjustment	(762)				(762)
Repurchases of common stock	$ (4,391)		(4,391)
Repurchases of common stock (in shares)	(80,189)	(172,000)
Ending balance at Jun. 30, 2016	$ 249,990	$ 26	$ 122,651	$ 191,907	$ (64,594)	$ 0
Ending balance (in shares) at Jun. 30, 2016		25,620,000