Earnings per Share - Number of Shares Outstanding for Calculation of Earnings Per Share (Detail) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2023	Mar. 31, 2022
Earnings Per Share [Abstract]
Net loss attributable to CECO Environmental Corp.	$ 1,978	$ 2,792
Denominator
Basic weighted-average shares outstanding	34,441,905	35,051,034
Common stock equivalents arising from stock options and restricted stock awards	757,000	148,000
Diluted weighted-average shares outstanding	35,198,668	35,199,201