Note 12 - Related Party Transactions (Details Textual) $ in Thousands	12 Months Ended
Dec. 31, 2019 USD ($)
American Bailey Corporation (ABC) [Member]
Sublease Income	$ 165
Lessor, Operating Lease, Payments to be Received, Total	$ 27
American Bailey Corporation (ABC) [Member] \| Fuel Tech, Inc. [Member]
Equity Method Investment, Ownership Percentage	27.00%

The percentage of ownership of common stock or equity participation in the investee accounted for under the equity method of accounting.

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- Definition

Amount of lease payments to be received by lessor for operating lease.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 842
-SubTopic 30
-Section 50
-Paragraph 12
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- Definition

Amount of sublease income excluding finance and operating lease expense.

+ References

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-Name Accounting Standards Codification
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