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Note 5 - Contract Assets and Contract Liabilities (Details Textual) - USD ($)
3 Months Ended
Mar. 31, 2019
Mar. 31, 2018
Dec. 31, 2018
Contract with Customer, Asset, Net, Current, Total $ 1,492,000 $ 1,244,000  
Increase (Decrease) in Contract with Customer, Asset (475,000) 282,000  
Contract with Customer, Liability, Current $ 475,000 $ 76,000 $ 1,004,000