Loss Per Share - Calculation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands				12 Months Ended
		Aug. 15, 2019	May 15, 2019	Oct. 31, 2021	Oct. 31, 2020	Oct. 31, 2019
Numerator
Net loss attributable to FuelCell Energy, Inc.				$ (101,055)	$ (89,107)	$ (77,568)
Warrant exchange				15,974	37,086
Preferred dividends - Series B				(3,200)	(3,331)	(3,231)
Net loss attributable to common stockholders				$ (104,255)	$ (92,438)	$ (100,245)
Denominator
Weighted average common shares outstanding - basic				334,742,346	221,960,288	55,081,266
Weighted average common shares outstanding - diluted				334,742,346	221,960,288	55,081,266
Net loss to common stockholders per share - basic				$ (0.31)	$ (0.42)	$ (1.82)
Net loss to common stockholders per share - diluted	[1]			$ (0.31)	$ (0.42)	$ (1.82)
Series A Preferred Stock
Numerator
Warrant exchange						$ (3,169)
Series B Preferred Stock
Numerator
Preferred dividends - Series B		$ 0	$ 0	$ (3,200)	$ (3,331)	(3,231)
Series C Preferred Stock
Numerator
Preferred stock deemed dividends and redemption value adjustments, net						(6,522)
Series D Preferred Stock
Numerator
Series D Preferred stock deemed dividends and redemption accretion						$ 9,755

[1] Due to the net loss to common stockholders in each of the years presented above, diluted earnings per share was computed without consideration to potentially dilutive instruments as their inclusion would have been antidilutive.