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	12 Months Ended
	Dec. 31, 2020	Dec. 31, 2019
Business Acquisition [Line Items]
Net sales	$ 329,801	$ 368,027
Net income attributable to CECO Environmental Corp	$ 9,728	$ 26,980
Income (loss) per share:
Basic	$ 0.28	$ 0.77
Diluted	$ 0.27	$ 0.76