Computation of Basic and Diluted Earnings (Loss) Per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2017		Dec. 31, 2016	Dec. 31, 2015
Numerators:
Income from continuing operations	$ 62,307		$ 22,003	$ 35,628
Less: Net income attributable to noncontrolling interest	(2,256)
Income from continuing operations attributable to Novanta Inc.	60,051		22,003	35,628
Less: Adjustment of redeemable noncontrolling interest to estimated redemption value (see Note 17)	(20,244)	[1]	0
Income from continuing operations attributable to Novanta Inc. after adjustment of redeemable noncontrolling interest to estimated redemption value	39,807		22,003	35,628
Loss from discontinued operations				(13)
Net income attributable to Novanta Inc. after adjustment of redeemable noncontrolling interest to estimated redemption value	$ 39,807		$ 22,003	$ 35,615
Denominators:
Weighted average common shares outstanding—basic	34,817		34,694	34,579
Dilutive potential common shares	463		220	248
Weighted average common shares outstanding— diluted	35,280		34,914	34,827
Antidilutive common shares excluded from above			85
Basic Earnings (Loss) per Common Share:
From continuing operations	$ 1.14		$ 0.63	$ 1.03
From discontinued operations				0.00
Basic earnings (loss) per share attributable to Novanta Inc.	1.14		0.63	1.03
Diluted Earnings (Loss) per Common Share:
From continuing operations	1.13		0.63	1.02
From discontinued operations				0.00
Diluted earnings (loss) per share attributable to Novanta Inc.	$ 1.13		$ 0.63	$ 1.02

[1] Adjustment of the carrying value of redeemable noncontrolling interest to the estimated redemption value was recognized in retained earnings instead of the consolidated statement of operations but was included in the computation of earnings per share attributable to Novanta Inc. (see Note 9).