Debt and Financing Obligation - Additional Information (Details) $ / shares in Units, shares in Millions					1 Months Ended			3 Months Ended	9 Months Ended	12 Months Ended
	Nov. 22, 2019 USD ($) $ / shares MW shares	May 09, 2019 USD ($) MW	Feb. 28, 2019 USD ($) MW	Jan. 09, 2019 USD ($)	Apr. 30, 2019 USD ($)	Jan. 31, 2019 USD ($) Position Employee	Oct. 31, 2015 USD ($) Position	Jan. 31, 2020 USD ($)	Jan. 31, 2020 USD ($)	Oct. 31, 2019 USD ($)	Dec. 31, 2019 USD ($)	May 16, 2019	May 08, 2019	Feb. 06, 2019 USD ($)	Nov. 30, 2016 USD ($)
Debt Instrument [Line Items]
Long-term line of credit, discount								$ 5,704,000	$ 5,704,000	$ 4,251,000
Class of warrants or rights issued value										$ 3,900,000
Minimum [Member] | Groton CT [Member]
Debt Instrument [Line Items]
Disposition,refinancing or tax equity investment consummated								$ 30,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member]
Debt Instrument [Line Items]
Percentage of aggregate principal amount on discount										2.50%
Percentage of cash interest paid								9.90%
Percentage of payment-in-kind interest								2.05%
Class of warrants or rights issued value										$ 3,900,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Groton CT [Member]
Debt Instrument [Line Items]
Disposition,refinancing or tax equity investment consummated								$ 30,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Tulare BioMAT [Member]
Debt Instrument [Line Items]
Disposition,refinancing or tax equity investment consummated								$ 5,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Senior Secured Credit Facility [Member]
Debt Instrument [Line Items]
Long-term Line of Credit										200,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Initial Funding [Member]
Debt Instrument [Line Items]
Drew down to fully repay debt outstanding										14,500,000
Long-term line of credit after discount										14,100,000
Long-term line of credit, discount										400,000
Debt instrument term								7 years
Quarterly payment payable period								1 year
Quarterly payment payable date								Oct. 31, 2027
Debt instrument, description								Outstanding principal under the Orion Facility will be amortized on a straight-line basis over a seven year term in quarterly payments beginning one year after the Initial Funding, with the initial payment due 21 business days after the end of the first quarter of fiscal 2021; provided that, if the Company does not have sufficient cash on hand to make any required quarterly amortization payments, such amounts shall be deferred and payable at such time as sufficient cash is available to make such payments subject to all outstanding principal being due and payable on the maturity date, which is the date that is eight years after the date of the Initial Funding or October 31, 2027.
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member]
Debt Instrument [Line Items]
Drew down to fully repay debt outstanding	$ 65,500,000
Long-term line of credit after discount	63,900,000
Long-term line of credit, discount	$ 1,600,000
Credit agreement requires to establish debt reserve								$ 5,000,000	5,000,000
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member] | Exercise Price 0.242 [Member]
Debt Instrument [Line Items]
Class of warrants or rights exercised | shares	8.0
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 0.242
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member] | Exercise Price 0.620 [Member]
Debt Instrument [Line Items]
Class of warrants or rights exercised | shares	6.0
Class of Warrant or Right, Exercise Price of Warrants or Rights | $ / shares	$ 0.620
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member] | Maximum [Member]
Debt Instrument [Line Items]
Class of warrants or rights issued | shares	14.0
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member] | Groton Project [Member]
Debt Instrument [Line Items]
Capacity of plant | MW	7.4
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member] | LIPA Yaphank Solid Waste Management Project [Member]
Debt Instrument [Line Items]
Capacity of plant | MW	7.4
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Second Funding [Member] | Tulare BioMAT [Member]
Debt Instrument [Line Items]
Capacity of plant | MW	2.8
Orion Energy Partners Investment Agent, LLC Credit Facility [Member] | Remainder of Funding [Member]
Debt Instrument [Line Items]
Line of credit receivable amount								120,000,000	120,000,000	120,000,000
Connecticut Green Bank Loans [Member]
Debt Instrument [Line Items]
Long-term Line of Credit								4,800,000	$ 4,800,000
Line of credit facility, maximum borrowing capacity										1,800,000	$ 3,000,000
Accrued fees payable		$ 400,000
Debt instrument, interest rate, stated percentage rate													5.00%
Debt instrument, interest rate, increase									8.00%
Connecticut Green Bank Loans [Member] | Groton Commitment Letter [Member]
Debt Instrument [Line Items]
Subordinated project term loan														$ 5,000,000
Subordinated Credit Agreement [Member] | Bridgeport Fuel Cell, LLC [Member] | Connecticut Green Bank Loans [Member]
Debt Instrument [Line Items]
Long-term Line of Credit								$ 5,600,000	$ 5,600,000
Capacity of plant | MW		14.9
Debt instrument, interest rate, stated percentage rate		8.00%
Proceeds from long-term lines of credit		$ 6,000,000
Debt instrument, covenant terms								On May 9, 2019, in connection with the closing of the purchase of the membership interests of Bridgeport Fuel Cell, LLC (“BFC”) (and the 14.9 MW Bridgeport Fuel Cell Project), BFC entered into a subordinated credit agreement with the Connecticut Green Bank whereby Connecticut Green Bank provided financing in the amount of $6.0 million (the “Subordinated Credit Agreement”). This $6.0 million consisted of $1.8 million in incremental funding that was received by BFC and $4.2 million of funding previously received by FuelCell Energy, Inc. with respect to which BFC became the primary obligor. As security for the Subordinated Credit Agreement, Connecticut Green Bank received a perfected lien, subordinated and second in priority to the liens securing the $25.0 million loaned under the BFC Credit Agreement (as defined below), in all of the same collateral securing the BFC Credit Agreement. The interest rate under the Subordinated Credit Agreement is 8% per annum. Principal and interest are due monthly in amounts sufficient to fully amortize the loan over an 84 month period ending in May 2026. The Subordinated Credit Agreement contains representations, warranties and covenants. The balance under the Subordinated Credit Agreement as of January 31, 2020 was $5.6 million.
Subordinated Credit Agreement [Member] | Incremental Funding [Member] | Bridgeport Fuel Cell, LLC [Member] | Connecticut Green Bank Loans [Member]
Debt Instrument [Line Items]
Proceeds from long-term lines of credit		1,800,000
Subordinated Credit Agreement [Member] | Senior Term Loan [Member] | Bridgeport Fuel Cell, LLC [Member] | Connecticut Green Bank Loans [Member]
Debt Instrument [Line Items]
Liens securing senior term loan amount		25,000,000
Subordinated Credit Agreement [Member] | Previously Received [Member] | Bridgeport Fuel Cell, LLC [Member] | Connecticut Green Bank Loans [Member]
Debt Instrument [Line Items]
Proceeds from long-term lines of credit		$ 4,200,000
Credit Agreement [Member] | Bridgeport Loans [Member]
Debt Instrument [Line Items]
Maturity date		May 09, 2025
Interest rate description								The interest rate under the BFC Credit Agreement fluctuates monthly at the 30-day LIBOR rate plus 275 basis points
Debt instrument, interest rate basis term		30 days
Credit Agreement [Member] | Bridgeport Loans [Member] | Interest Rate Swap
Debt Instrument [Line Items]
Net interest rate												5.09%
Credit Agreement [Member] | Bridgeport Loans [Member] | Level Adjustments [Member] | Interest Rate Swap
Debt Instrument [Line Items]
Fair value adjustments								$ 30,000
Credit Agreement [Member] | Bridgeport Fuel Cell, LLC [Member]
Debt Instrument [Line Items]
Debt instrument, total notional value		$ 25,000,000
Credit Agreement [Member] | Bridgeport Fuel Cell, LLC [Member] | Bridgeport Loans [Member] | Fifth Third Bank [Member]
Debt Instrument [Line Items]
Proceeds from long-term lines of credit		12,500,000
Credit Agreement [Member] | Bridgeport Fuel Cell, LLC [Member] | Bridgeport Loans [Member] | Liberty Bank [Member]
Debt Instrument [Line Items]
Proceeds from long-term lines of credit		$ 12,500,000
Finance Obligations for Sale Leaseback Agreements [Member] | PNC Energy Capital, LLC [Member]
Debt Instrument [Line Items]
Long-term Line of Credit								44,800,000	44,800,000	45,200,000
State of Connecticut [Member]
Debt Instrument [Line Items]
Long-term Line of Credit								9,864,000	9,864,000	10,000,000
Debt instrument term							15 years
Debt instrument, interest rate, stated percentage rate							2.00%
Debt instrument, total notional value							$ 10,000,000	$ 10,000,000	$ 10,000,000
Debt instrument, payment terms, period principal payments are deferred							4 years
Debt instrument, date of first required payment							Dec. 01, 2019
Loan forgiveness terms								if the Company created 165 full-time positions and retained 538 full-time positions for two consecutive years (the “Employment Obligation”) as measured on October 28, 2017 (the “Target Date”). The Assistance Agreement was subsequently amended in April 2017 to extend the Target Date by two years to October 28, 2019
State of Connecticut [Member] | Employment Obligation [Member]
Debt Instrument [Line Items]
Number of full time positions required to be created | Position							165
Number of full time positions required to be retained | Position							538
State of Connecticut [Member] | Maximum [Member]
Debt Instrument [Line Items]
Percentage of loan forgiveness								5.00%
State of Connecticut [Member] | Second Amendment [Member] | Employment Obligation [Member]
Debt Instrument [Line Items]
Number of minimum full time positions required to be maintained | Employee						538
Number of consecutive months maintain the full time positions						24 months
Additional number of full time positions required to be create | Position						91
Additional credits to be earned						$ 2,000,000
Target date of job audit						90 days
Principal payable number of employee under employee obligation target						$ 18,587.36
Webster Bank Term Loan [Member]
Debt Instrument [Line Items]
Debt instrument, interest rate, stated percentage rate range								5.00%
Notes payable to bank, current										500,000					$ 2,300,000
Enhanced Capital Term Loan and Security Agreement [Member]
Debt Instrument [Line Items]
Long-term Line of Credit										1,500,000
Line of credit facility, maximum borrowing capacity				$ 1,500,000
Interest rate, basis points				6.00%
Debt instrument, maturity period description								The loan maturity date was three years from the date of the Enhanced Capital Loan Agreement, upon which the outstanding principal and any accrued interest would be due and payable.
Debt instrument, maturity period				3 years
New Construction Loan Facility [Member] | Fifth Third Bank Groton Loan [Member]
Debt Instrument [Line Items]
Total outstanding balance										$ 11,100,000
New Construction Loan Facility [Member] | Fifth Third Bank Groton Loan [Member]
Debt Instrument [Line Items]
Line of credit facility, maximum borrowing capacity			$ 23,000,000
Loan advance			$ 9,700,000		$ 1,400,000
New Construction Loan Facility [Member] | Groton CT [Member] | Fifth Third Bank Groton Loan [Member]
Debt Instrument [Line Items]
Capacity of plant | MW			7.4
PNC Energy Capital, LLC [Member]
Debt Instrument [Line Items]
Debt instrument term								10 years
Bridgeport Fuel Cell, LLC [Member]
Debt Instrument [Line Items]
Debt instrument term								8 years
Orion Credit Facility [Member]
Debt Instrument [Line Items]
Debt instrument term								8 years