Loss Per Share - Calculation of Basic and Diluted Loss Per Share (Details) - USD ($) $ / shares in Units, $ in Thousands	3 Months Ended						9 Months Ended
	Jul. 31, 2022	Apr. 30, 2022	Jan. 31, 2022	Jul. 31, 2021	Apr. 30, 2021	Jan. 31, 2021	Jul. 31, 2022	Jul. 31, 2021
Numerator
Net loss attributable to FuelCell Energy, Inc.	$ (29,414)			$ (11,997)			$ (100,255)	$ (76,874)
Preferred dividends - Series B	(800)	$ (800)	$ (800)	(800)	$ (800)	$ (800)
Net loss attributable to common stockholders	$ (30,214)			$ (12,797)			$ (102,655)	$ (79,274)
Denominator
Weighted average common shares outstanding - basic	387,465,758			337,291,562			375,638,293	323,983,465
Weighted average common shares outstanding - diluted	387,465,758			337,291,562			375,638,293	323,983,465
Net loss to common stockholders per share - basic	$ (0.08)			$ (0.04)			$ (0.27)	$ (0.24)
Net loss to common stockholders per share - diluted	$ (0.08)			$ (0.04)			$ (0.27)	$ (0.24)
Series B Preferred Stock
Numerator
Preferred dividends - Series B	$ (800)			$ (800)			$ (2,400)	$ (2,400)