Computation of Basic and Diluted Earnings per Share (Details) - USD ($) $ / shares in Units, shares in Thousands, $ in Thousands	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Numerators:
Consolidated net income	$ 51,095	$ 62,307	$ 22,003
Less: Net income attributable to noncontrolling interest	(1,986)	(2,256)
Net income attributable to Novanta Inc.	49,109	60,051	22,003
Redeemable noncontrolling interest redemption value adjustment (Note 5)	1,781	(20,244)
Net income attributable to Novanta Inc. after adjustment for redeemable noncontrolling interest redemption value	$ 50,890	$ 39,807	$ 22,003
Denominators:
Weighted average common shares outstanding—basic	34,913	34,817	34,694
Dilutive potential common shares	560	463	220
Weighted average common shares outstanding— diluted	35,473	35,280	34,914
Antidilutive common shares excluded from above	4		85
Earnings per Common Share Attributable to Novanta Inc.:
Basic	$ 1.46	$ 1.14	$ 0.63
Diluted	$ 1.43	$ 1.13	$ 0.63