Acquisitions and Joint Ventures - Schedule of Unaudited Pro Forma Financial Information (Details) - Environmental Integrated Solutions and Mader Holdings L.P. [Member] - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended
	Mar. 31, 2021	Mar. 31, 2020
Business Acquisition [Line Items]
Net sales	$ 71,892	$ 88,799
Net income attributable to CECO Environmental Corp	$ 1,181	$ 4,363
Earnings per share:
Basic	$ 0.03	$ 0.12
Diluted	$ 0.03	$ 0.12