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Note 3 - Significant Accounting Policies - Estimated Useful Lives of Assets (Details)
6 Months Ended
Jun. 30, 2019
Building and Building Improvements [Member] | Minimum [Member]  
Estimated useful life (Year) 10 years
Building and Building Improvements [Member] | Maximum [Member]  
Estimated useful life (Year) 44 years
Tenant Improvements [Member]  
Estimated useful life Shorter of useful life or lease term
Furniture, Fixtures and Equipment [Member] | Minimum [Member]  
Estimated useful life (Year) 3 years
Furniture, Fixtures and Equipment [Member] | Maximum [Member]  
Estimated useful life (Year) 15 years