Loss Per Share - Schedule of Calculation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended		6 Months Ended
	Apr. 30, 2024	Apr. 30, 2023	Apr. 30, 2024	Apr. 30, 2023
Numerator
Net loss attributable to FuelCell Energy, Inc.	$ (32,140)	$ (34,303)	$ (51,933)	$ (52,925)
Series B preferred stock dividends	(800)	(800)	(1,600)	(1,600)
Net loss attributable to common stockholders	$ (32,940)	$ (35,103)	$ (53,533)	$ (54,525)
Denominator
Weighted average common shares outstanding - basic	452,984,445	406,316,070	452,303,339	406,055,027
Weighted average common shares outstanding - diluted	452,984,445	406,316,070	452,303,339	406,055,027
Net loss to common stockholders per share - basic	$ (0.07)	$ (0.09)	$ (0.12)	$ (0.13)
Net loss to common stockholders per share - diluted	$ (0.07)	$ (0.09)	$ (0.12)	$ (0.13)
Series B Preferred Stock
Numerator
Series B preferred stock dividends	$ (800)	$ (800)	$ (1,600)	$ (1,600)