Computation of Basic and Diluted Earnings per Common Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	3 Months Ended
	Mar. 30, 2018	Mar. 31, 2017
Numerators:
Consolidated net income	$ 12,837	$ 34,274
Less: Net income attributable to noncontrolling interest	(926)	(22)
Net income attributable to Novanta Inc.	11,911	34,252
Less: Adjustment of redeemable noncontrolling interest to estimated redemption value (see Note 14)	(5,399)
Net income attributable to Novanta Inc. after adjustment of redeemable noncontrolling interest to estimated redemption value	$ 6,512	$ 34,252
Denominators:
Weighted average common shares outstanding—basic	34,887	34,765
Dilutive potential common shares	541	360
Weighted average common shares outstanding— diluted	35,428	35,125
Antidilutive common shares excluded from above	12
Earnings per Common Share Attributable to Novanta Inc.:
Basic	$ 0.19	$ 0.99
Diluted	$ 0.18	$ 0.98