Consolidated Statement of Stockholders' Equity (USD $) In Thousands, except Share data, unless otherwise specified	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, 2012	$ 232,012	$ 27	$ 152,188	$ 103,200	$ (23,403)	$ 1,239
Beginning balance, shares at Dec. 31, 2012		26,724,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock	1,767		1,767
Stock-based compensation and vesting of restricted stock, Shares		19,000
Net income attributable to Altra Industrial Motion Corp.	22,569			22,569
Net loss attributable to non-controlling interest	34					(34)
Dividends declared	(4,863)			(4,863)
Change in fair value of interest rate swap	537				537
Cumulative foreign currency translation adjustment	(6,681)				(6,681)
Ending balance at Jun. 29, 2013	245,341	27	153,955	120,906	(29,547)	1,205
Ending balance, shares at Jun. 29, 2013		26,743,000
Beginning balance at Dec. 31, 2013	269,333	27	154,471	133,231	(18,396)	991
Beginning balance, shares at Dec. 31, 2013		26,820,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock-based compensation and vesting of restricted stock	1,698		1,698
Stock-based compensation and vesting of restricted stock, Shares		24,000
Net income attributable to Altra Industrial Motion Corp.	24,162			24,162
Net loss attributable to non-controlling interest	(19)					19
Dividends declared	(5,949)			(5,949)
Change in fair value of interest rate swap	(120)				(120)
Cumulative foreign currency translation adjustment	904				904	74
Repurchase of common stock	(2,907)		(2,907)
Repurchase of common stock, shares		(81,642)
Ending balance at Jun. 30, 2014	$ 287,121	$ 27	$ 153,262	$ 151,444	$ (17,612)	$ 1,084
Ending balance, shares at Jun. 30, 2014		26,762,000