Earnings per Share - Number of Shares Outstanding for Calculation of Earnings Per Share (Detail) - USD ($) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2023	Jun. 30, 2022	Jun. 30, 2023	Jun. 30, 2022
Earnings Per Share [Abstract]
Net loss attributable to CECO Environmental Corp.	$ 3,724	$ 4,385	$ 5,701	$ 7,180
Denominator
Basic weighted-average shares outstanding	34,619,216	34,873,238	34,531,050	34,961,645
Common stock equivalents arising from stock options and restricted stock awards	525,000	168,000	641,000	158,000
Diluted weighted-average shares outstanding	35,143,782	35,041,152	35,171,727	35,119,685