Note 2 - Summary of Significant Accounting Policies (Tables)

6 Months Ended

Jun. 30, 2025

Debt Securities, Held-to-Maturity [Table Text Block]

	As of
Held-to-maturity debt securities:	June 30, 2025			December 31, 2024
Amortized cost	$	20,345		$	21,059
Gross unrecognized gains		67			50
Gross unrecognized losses		(7	)		(33	)
Fair value	$	20,405		$	21,076

Investments Classified by Contractual Maturity Date [Table Text Block]

	Amortized Cost		Fair Value
Within one year	$	12,420	$	12,455
After one year through two years		6,943		6,955
After two years through three years		982		995
Total	$	20,345	$	20,405

Financing Receivable, Allowance for Credit Loss [Table Text Block]

At January 1, 2024	$	111
Provision charged to expense		—
(Write-offs) / Recoveries		(5	)
At December 31, 2024	$	106
Provision charged to expense		—
(Write-offs) / Recoveries		2
At June 30, 2025	$	108

- Definition

Tabular disclosure of information about investment in debt security measured at amortized cost (held-to-maturity).

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 320
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-URI https://asc.fasb.org/1943274/2147481800/320-10-50-5

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
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+ Details

FUEL TECH, INC. 10-Q