Acquisitions and Joint Ventures - Schedule of Unaudited Pro Forma Financial Information (Details) - Environmental Integrated Solutions [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2021	Jun. 30, 2020	Jun. 30, 2021	Jun. 30, 2020
Business Acquisition [Line Items]
Net sales	$ 78,680	$ 79,809	$ 150,572	$ 168,608
Net income attributable to CECO Environmental Corp.	$ 293	$ 3,834	$ 1,474	$ 8,198
Earnings per share:
Basic	$ 0.01	$ 0.11	$ 0.04	$ 0.23
Diluted	$ 0.01	$ 0.11	$ 0.04	$ 0.23