Computation of Basic and Diluted Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 29, 2018	Jun. 30, 2017	Jun. 29, 2018	Jun. 30, 2017
Numerators:
Consolidated net income	$ 11,625	$ 9,990	$ 24,462	$ 44,264
Less: Net income attributable to noncontrolling interest	(625)	(588)	(1,551)	(610)
Net income attributable to Novanta Inc.	11,000	9,402	22,911	43,654
Decrease (increase) in estimated redemption value of redeemable noncontrolling interest (see Note 15)	303	(3,718)	(5,096)	(3,718)
Net income attributable to Novanta Inc. after adjustment of redeemable noncontrolling interest to estimated redemption value	$ 11,303	$ 5,684	$ 17,815	$ 39,936
Denominators:
Weighted average common shares outstanding—basic	34,949	34,827	34,919	34,796
Dilutive potential common shares	525	636	532	498
Weighted average common shares outstanding— diluted	35,474	35,463	35,451	35,294
Antidilutive common shares excluded from above			6
Earnings per Common Share Attributable to Novanta Inc.:
Basic	$ 0.32	$ 0.16	$ 0.51	$ 1.15
Diluted	$ 0.32	$ 0.16	$ 0.50	$ 1.13