Nature of Business and Summary of Significant Accounting Policies - Schedule of Numerators and Denominators Used to Calculate Basic and Diluted Earnings Per Share (Detail) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2021	Dec. 31, 2020	Dec. 31, 2019
Numerator (for basic and diluted earnings per share)
Net income attributable to CECO Environmental Corp.	$ 1,426	$ 8,211	$ 17,707
Denominator
Basic weighted-average shares outstanding	35,345,785	35,289,616	34,987,878
Common stock equivalents arising from stock options and restricted stock awards	249,000	231,000	496,000
Diluted weighted-average shares outstanding	35,594,779	35,520,670	35,484,273