Note 3 - Revenue - Components of Accounts Receivable (Details) - USD ($) $ in Thousands	Jun. 30, 2024	Dec. 31, 2023	Dec. 31, 2022
Trade receivables	$ 5,182	$ 4,300
Unbilled receivables	1,543	2,285
Receivable for employee retention credit	1,677	0
Other short-term receivables	355	255
Allowance for credit losses	(106)	(111)	$ (110)
Total accounts receivable	$ 8,651	$ 6,729

Represents the receivable for the Employee Retention Credit ("ERC").

No definition available.

Name:	ftek_EmployeeRetentionCreditReceivable
Namespace Prefix:	ftek_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Amount, after allowance, receivable from customers, clients, or other third-parties, and receivables classified as other due within one year or the normal operating cycle, if longer.

+ References

No definition available.

+ Details

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

- Definition

Amount, before allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

+ References

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

Amount, after allowance for credit loss, of right to consideration from customer for product sold and service rendered in normal course of business, classified as current.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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- Definition

Amount of allowance for credit loss on accounts receivable.

+ References

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+ Details

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

- Definition

Amount received for services rendered and products shipped, but not yet billed, for non-contractual agreements due within one year or the normal operating cycle, if longer.

+ References

No definition available.

+ Details

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