Consolidated Statements of Changes in Equity - USD ($) $ in Thousands	Total	Series D Preferred Stock [Member]	Series C Preferred Stock [Member]	Common Stock [Member]	Additional Paid-in Capital [Member]	Additional Paid-in Capital [Member] Series D Preferred Stock [Member]	Additional Paid-in Capital [Member] Series C Preferred Stock [Member]	Accumulated Deficit [Member]	Accumulated Other Comprehensive Income (Loss) [Member]	Treasury Stock [Member]	Deferred Compensation [Member]
Balance at at Oct. 31, 2017	$ 101,256			$ 1	$ 1,045,203			$ (943,533)	$ (415)	$ (280)	$ 280
Balance at (in shares) at Oct. 31, 2017				5,791,068
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of warrants	2,647				2,647
Exercise of warrants, (in shares)				172,200
Share based compensation	617				617
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(75)				(75)
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans, (in shares)				(8,912)
Series C convertible preferred stock conversions	7,569				7,569
Series C convertible preferred stock conversions, (in shares)				512,487
Preferred stock dividends	(800)				(800)
Effect of foreign currency translation	33								33
Net loss attributable to FuelCell Energy, Inc.	(4,183)							(4,183)
Balance at at Jan. 31, 2018	107,064			$ 1	1,055,161			(947,716)	(382)	(280)	280
Balance at (in shares) at Jan. 31, 2018				6,466,843
Balance at at Oct. 31, 2017	101,256			$ 1	1,045,203			(943,533)	(415)	(280)	280
Balance at (in shares) at Oct. 31, 2017				5,791,068
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Series C convertible preferred stock conversions, (in shares)			3,914,218
Effect of foreign currency translation	(41)
Net loss attributable to FuelCell Energy, Inc.	(33,238)
Balance at at Jul. 31, 2018	95,508			$ 1	1,072,734			(976,771)	(456)	(447)	447
Balance at (in shares) at Jul. 31, 2018				7,690,014
Balance at at Jan. 31, 2018	107,064			$ 1	1,055,161			(947,716)	(382)	(280)	280
Balance at (in shares) at Jan. 31, 2018				6,466,843
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Exercise of warrants	621				621
Exercise of warrants, (in shares)				44,109
Common stock issued, non-employee compensation	282				282
Common stock issued, non-employee compensation, (in shares)				10,066
Share based compensation	761				761
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(546)				(546)
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans, (in shares)				(1,282)
Series C convertible preferred stock conversions	8,029				8,029
Series C convertible preferred stock conversions, (in shares)				559,844
Preferred stock dividends	(800)				(800)
Effect of foreign currency translation	54								54
Adjustment for deferred compensation											167
Adjustment for deferred compensation, (in shares)				(4,683)
Adjustment for deferred compensation										(167)
Net loss attributable to FuelCell Energy, Inc.	(13,174)							(13,174)
Balance at at Apr. 30, 2018	102,291			$ 1	1,063,508			(960,890)	(328)	(447)	447
Balance at (in shares) at Apr. 30, 2018				7,074,897
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of common stock, net of fees	6,745				6,745
Sale of common stock, net of fees (in shares)				435,329
Share based compensation	931				931
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(35)				(35)
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans, (in shares)				1,403
Series C convertible preferred stock conversions	2,385				2,385
Series C convertible preferred stock conversions, (in shares)				181,191
Preferred stock dividends	(800)				(800)
Effect of foreign currency translation	(128)								(128)
Net loss attributable to FuelCell Energy, Inc.	(15,881)							(15,881)
Balance at at Jul. 31, 2018	95,508			$ 1	1,072,734			(976,771)	(456)	(447)	447
Balance at (in shares) at Jul. 31, 2018				7,690,014
Balance at at Oct. 31, 2018	$ 82,194			$ 1	1,073,463			(990,867)	(403)	(363)	363
Balance at (in shares) at Oct. 31, 2018	7,972,686			7,972,686
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Share based compensation	$ 987				987
Fee adjustment for common stock issuance	90				90
Common stock issued under benefit plans, net of taxes paid upon vesting of restricted stock awards	27				27
Common stock issued under benefit plans, net of taxes paid upon vesting of restricted stock awards, (in shares)				1,946
Series C convertible preferred stock conversions	1,974				1,974
Series C convertible preferred stock conversions, (in shares)				127,829
Series C convertible preferred stock adjustment for beneficial conversion feature	6,586				6,586
Series C convertible stock redemption value adjustments	(8,550)				(8,550)
Series D convertible preferred stock conversions	4,334				4,334
Series D convertible preferred stock conversions, (in shares)				932,144
Convertible preferred stock redemption accretion		$ (3,793)				$ (3,793)
Preferred stock dividends	(800)				(800)
Impact of the adoption of Topic 606	(6,654)							(6,654)
Effect of foreign currency translation	7								7
Net loss attributable to FuelCell Energy, Inc.	(17,548)							(17,548)
Balance at at Jan. 31, 2019	58,854			$ 1	1,074,318			(1,015,069)	(396)	(363)	363
Balance at (in shares) at Jan. 31, 2019				9,034,605
Balance at at Oct. 31, 2018	$ 82,194			$ 1	1,073,463			(990,867)	(403)	(363)	363
Balance at (in shares) at Oct. 31, 2018	7,972,686			7,972,686
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Effect of foreign currency translation	$ (28)
Net loss attributable to FuelCell Energy, Inc.	(42,389)
Balance at at Jul. 31, 2019	$ 84,883			$ 12	1,125,212			(1,039,910)	(431)	(466)	466
Balance at (in shares) at Jul. 31, 2019	118,387,637			118,387,637
Balance at at Jan. 31, 2019	$ 58,854			$ 1	1,074,318			(1,015,069)	(396)	(363)	363
Balance at (in shares) at Jan. 31, 2019				9,034,605
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Common stock issued, non-employee compensation	102				102
Common stock issued, non-employee compensation, (in shares)				29,454
Share based compensation	955				955
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(219)				(219)
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans, (in shares)				52,784
Series A warrant exchange, (in shares)				500,000
Series C convertible preferred stock conversions	10,355				10,355
Series C convertible preferred stock conversions, (in shares)				2,127,528
Series D convertible preferred stock conversions	6,305				6,305
Series D convertible preferred stock conversions, (in shares)				1,994,413
Convertible preferred stock redemption accretion			$ (6,047)				$ (6,047)
Preferred stock dividends	(800)				(800)
Effect of foreign currency translation	(140)								(140)
Adjustment for deferred compensation											103
Adjustment for deferred compensation, (in shares)				(29,454)
Adjustment for deferred compensation										(103)
Net loss attributable to FuelCell Energy, Inc.	(19,530)							(19,530)
Balance at at Apr. 30, 2019	49,835			$ 1	1,084,969			(1,034,599)	(536)	(466)	466
Balance at (in shares) at Apr. 30, 2019				13,709,330
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Sale of common stock, net of fees	16,199			$ 3	16,196
Sale of common stock, net of fees (in shares)				43,997,807
Share based compensation	383				383
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans	(9)				(9)
Taxes paid upon vesting of restricted stock awards, net of stock issued under benefit plans, (in shares)				437
Series C convertible preferred stock conversions	3,162			$ 2	3,160
Series C convertible preferred stock conversions, (in shares)			1,658,861	1,658,861
Series D convertible preferred stock conversions	20,519			$ 6	20,513
Series D convertible preferred stock conversions, (in shares)				59,021,202
Effect of foreign currency translation	105								105
Net loss attributable to FuelCell Energy, Inc.	(5,311)							(5,311)
Balance at at Jul. 31, 2019	$ 84,883			$ 12	$ 1,125,212			$ (1,039,910)	$ (431)	$ (466)	$ 466
Balance at (in shares) at Jul. 31, 2019	118,387,637			118,387,637