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Note 3 - Supplemental Balance Sheet Information (in Thousands) (Details Textual) - USD ($)
12 Months Ended
Dec. 31, 2020
Dec. 31, 2019
Finite-Lived Intangible Assets, Gross, Total $ 5,021,000 $ 5,021,000
Customer Contracts And Lists [Member]    
Finite-Lived Intangible Assets, Gross, Total 2,731,000 2,731,000
Amortization of Intangible Assets, Total $ 534,000 $ 476,000
Customer Contracts And Lists [Member] | Minimum [Member]    
Finite-Lived Intangible Asset, Useful Life (Year) 5 years  
Customer Contracts And Lists [Member] | Maximum [Member]    
Finite-Lived Intangible Asset, Useful Life (Year) 25 years