Computation of Basic and Diluted Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands		3 Months Ended		9 Months Ended
		Sep. 28, 2018	Sep. 29, 2017	Sep. 28, 2018	Sep. 29, 2017
Numerators:
Consolidated net income		$ 14,989	$ 8,366	$ 39,451	$ 52,630
Less: Net income attributable to noncontrolling interest		(435)	(834)	(1,986)	(1,444)
Net income attributable to Novanta Inc.		14,554	7,532	37,465	51,186
Redeemable noncontrolling interest redemption value adjustment (see Note 15)		6,877	(7,585)	1,781	(11,303)
Net income (loss) attributable to Novanta Inc. after adjustment for redeemable noncontrolling interest redemption value		$ 21,431	$ (53)	$ 39,246	$ 39,883
Denominators:
Weighted average common shares outstanding—basic		34,899	34,833	34,918	34,809
Dilutive potential common shares	[1],[2]	586		551	426
Weighted average common shares outstanding— diluted		35,485	34,833	35,469	35,235
Earnings (Loss) per Common Share Attributable to Novanta Inc.:
Basic		$ 0.61	$ 0.00	$ 1.12	$ 1.15
Diluted		$ 0.60	$ 0.00	$ 1.11	$ 1.13

[1] 53,968 non-GAAP EPS performance restricted stock units granted to certain members of the executive management team and 213,219 shares of restricted stock issued to Laser Quantum non-controlling interest holders (see Note 15) are considered contingently issuable shares and are excluded from the calculation of the denominator as the contingent conditions had not been met as of the end of each period presented.

[2] Due to the Company’s net loss position after adjustment of redeemable noncontrolling interest to estimated redemption value for the three months ended September 29, 2017, all potentially dilutive shares are excluded from the calculation of the denominator as their effect would have been anti-dilutive.