Common Stock Reserved For Settlement of Restricted Stock Units.

No definition available.

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Namespace Prefix:	fcel_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Increase in common stock shares authorized.

+ References

No definition available.

+ Details

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Namespace Prefix:	fcel_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility agreed to pay option premium in exchange for agreement payable.

+ References

No definition available.

+ Details

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Namespace Prefix:	fcel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line of credit facility percentage of discount for each draw.

+ References

No definition available.

+ Details

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Namespace Prefix:	fcel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility percentage of discount for each draw if not repaid within nine months.

+ References

No definition available.

+ Details

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Namespace Prefix:	fcel_
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Balance Type:	na
Period Type:	duration

- Definition

Line of credit facility percentage of discount for each draw if not repaid within six months.

+ References

No definition available.

+ Details

Name:	fcel_LineOfCreditFacilityPercentageOfDiscountForEachDrawIfNotRepaidWithinSixMonths
Namespace Prefix:	fcel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Loan forgiveness period.

+ References

No definition available.

+ Details

Name:	fcel_LoanForgivenessPeriod
Namespace Prefix:	fcel_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Loan forgiveness terms.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Percentage of cash interest paid.

+ References

No definition available.

+ Details

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Namespace Prefix:	fcel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of payment in kind interest.

+ References

No definition available.

+ Details

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Namespace Prefix:	fcel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of prepayment of credit facility upon issuance of debt.

+ References

No definition available.

+ Details

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Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of prepayment of credit facility upon issuance of equity.

+ References

No definition available.

+ Details

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Namespace Prefix:	fcel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage of proceeds used for payroll costs.

+ References

No definition available.

+ Details

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Namespace Prefix:	fcel_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Sales agreement termination date.

+ References

No definition available.

+ Details

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Namespace Prefix:	fcel_
Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Share based compensation arrangement by share based payment award grant-date fair value of awards.

+ References

No definition available.

+ Details

Name:	fcel_ShareBasedCompensationArrangementByShareBasedPaymentAwardGrantDateFairValueOfAwards
Namespace Prefix:	fcel_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The maximum number of common shares permitted to be issued by an entity's charter and bylaws.

+ References

+ Details

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 942
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-URI http://asc.fasb.org/extlink&oid=6876686&loc=d3e534808-122878

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-Publisher FASB
-Name Accounting Standards Codification
-Topic 944
-SubTopic 210
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(16))
-URI http://asc.fasb.org/extlink&oid=119400593&loc=d3e572229-122910

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Description of the terms of a credit facility arrangement. Terms typically include interest rate, collateral required, guarantees required, repayment requirements, and restrictions on use of assets and activities of the entity.

+ References

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility terminates, in CCYY-MM-DD format.

+ References

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Description of the frequency of periodic payments, which may be presented in a variety of ways (for example, monthly, quarterly, annually).

+ References

+ Details

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Date the credit facility first became available, in CCYY-MM-DD format.

+ References

+ Details

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Data Type:	xbrli:dateItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The cash inflow from a contractual arrangement with the lender, including letter of credit, standby letter of credit and revolving credit arrangements, under which borrowings can be made up to a specific amount at any point in time with maturities due beyond one year or the operating cycle, if longer.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 14
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=118932676&loc=d3e3255-108585

+ Details

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Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Number of additional shares authorized for issuance under share-based payment arrangement.

+ References

No definition available.

+ Details

Name:	us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfAdditionalSharesAuthorized
Namespace Prefix:	us-gaap_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of shares authorized for issuance under share-based payment arrangement.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 718
-SubTopic 10
-Section 50
-Paragraph 2
-Subparagraph (a)(3)
-URI http://asc.fasb.org/extlink&oid=116856206&loc=d3e5070-113901

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Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	instant

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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- Details

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Balance Type:
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- Details

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Period Type:

- Details

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- Details

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Balance Type:
Period Type:

- Details

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Subsequent Events - Additional Information (Details) - USD ($)						6 Months Ended
	Jun. 11, 2020	Jun. 05, 2020	May 08, 2020	Apr. 24, 2020	Apr. 20, 2020	Apr. 30, 2020	Jun. 08, 2020	May 11, 2020	May 10, 2020	Oct. 31, 2019
Subsequent Event [Line Items]
Common stock, shares authorized						225,000,000				225,000,000
Subsequent Event [Member]
Subsequent Event [Line Items]
Increase in the number of authorized shares			112,500,000
Common stock, shares authorized								337,500,000	225,000,000
Subsequent Event [Member] \| At Market Issuance Sales Agreement [Member] \| B. Riley FBR, Inc [Member]
Subsequent Event [Line Items]
Sales agreement termination date		Jun. 12, 2020
Subsequent Event [Member] \| 2018 Omnibus Incentive Plan [Member] \| Non-Employee Director [Member]
Subsequent Event [Line Items]
Number of Shares Authorized			4,333,333
Common stock reserved for settlement of restricted stock units			1,000,000
Minimum [Member] \| Subsequent Event [Member] \| 2018 Omnibus Incentive Plan [Member] \| Non-Employee Director [Member]
Subsequent Event [Line Items]
Grant-date fair value of awards			$ 200,000,000
Maximum [Member] \| Subsequent Event [Member] \| 2018 Omnibus Incentive Plan [Member]
Subsequent Event [Line Items]
Number of additional shares authorized			4,000,000
Maximum [Member] \| Subsequent Event [Member] \| 2018 Omnibus Incentive Plan [Member] \| Non-Employee Director [Member]
Subsequent Event [Line Items]
Grant-date fair value of awards			$ 250,000,000
Liberty Bank Promissory Note (PPP Note) [Member]
Subsequent Event [Line Items]
Long-term line of credit						$ 6,515,000
Liberty Bank Promissory Note (PPP Note) [Member] \| Liberty Bank [Member]
Subsequent Event [Line Items]
Loan forgiveness terms						In order to obtain the consent of the Agent and the Orion Lenders under the Orion Facility to enter into the PPP Note, the Agent and the Orion Lenders have required the Company to apply for forgiveness within 30 days after the last day of the loan forgiveness period as designated under the PPP regulations in effect as of June 6, 2020.
Liberty Bank Promissory Note (PPP Note) [Member] \| Liberty Bank [Member] \| CARES Act [Member]
Subsequent Event [Line Items]
Proceeds from long-term lines of credit				$ 6,500,000
Loan forgiveness terms						In order to obtain the consent of the Agent and the Orion Lenders under the Orion Facility to enter into the PPP Note, the Agent and the Orion Lenders have required the Company to apply for forgiveness within 30 days after the last day of the loan forgiveness period as designated under the PPP regulations in effect as of June 6, 2020. If we seek forgiveness of the loan, we must apply for such forgiveness by October 31, 2020.
Loan forgiveness period				56 days	56 days
Debt instrument term				2 years	2 years
Liberty Bank Promissory Note (PPP Note) [Member] \| Liberty Bank [Member] \| PPP Flexibility Act [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Loan forgiveness period		168 days
Debt instrument term		5 years
Liberty Bank Promissory Note (PPP Note) [Member] \| Minimum [Member] \| Liberty Bank [Member] \| CARES Act [Member]
Subsequent Event [Line Items]
Percentage of proceeds used for payroll expenditure				75.00%	75.00%	75.00%
Liberty Bank Promissory Note (PPP Note) [Member] \| Minimum [Member] \| Liberty Bank [Member] \| PPP Flexibility Act [Member] \| Subsequent Event [Member]
Subsequent Event [Line Items]
Percentage of proceeds used for payroll expenditure		60.00%
Orion Credit Agreement [Member] \| Senior Secured Credit Facility [Member]
Subsequent Event [Line Items]
Long-term line of credit										$ 200,000,000.0
Orion Credit Agreement [Member] \| Fifth Orion Amendment [Member]
Subsequent Event [Line Items]
Line of credit facility, description						The Secondary Facility Loan commitment allows the Company to draw on the Secondary Facility Loans commencing on June 5, 2020 (the “Commencement Date”) and terminating on September 14, 2020 (the “Termination Date”). The Company may make draws on the Secondary Facility Loans in amounts of no less than $5 million, and no more than $15 million may be drawn in any 30 day period, provided that the Company may draw any remaining available funds under the Secondary Facility Loans between August 15, 2020 and the Termination Date. Any drawn amounts must be fully repaid on or before September 1, 2021 (the “Secondary Facility Repayment Date”).
Orion Credit Agreement [Member] \| Subsequent Event [Member] \| Fifth Orion Amendment [Member]
Subsequent Event [Line Items]
Line of credit facility, maximum borrowing capacity	$ 35,000,000						$ 35,000,000
Line of credit facility, commencement date	Jun. 05, 2020
Line of credit facility, repayment date	Sep. 01, 2021
Agreed to pay option premium in exchange for loan commitment	$ 1,000,000
Percentage of discount for each draw	5.00%
Percentage of discount for each draw if not paid with in six months	10.00%
Percentage of discount for each draw if not paid with in nine months	20.00%
Percentage of cash interest paid	9.90%
Line of credit facility, frequency of payments	quarterly
Percentage of payment-in-kind interest	2.05%
Percentage of prepayment of credit facility upon issuance of debt	100.00%
Percentage of prepayment of credit facility upon issuance of equity	50.00%
Orion Credit Agreement [Member] \| Minimum [Member] \| Subsequent Event [Member] \| Fifth Orion Amendment [Member]
Subsequent Event [Line Items]
Amount may draws on the secondary facility loan	$ 5,000,000
Orion Credit Agreement [Member] \| Maximum [Member] \| Subsequent Event [Member] \| Fifth Orion Amendment [Member]
Subsequent Event [Line Items]
Amount may draws on the secondary facility loan	$ 15,000,000