Note 3 - Real Estate - Summary of Geographic Concentration of Properties (Details) $ in Thousands	6 Months Ended
Jun. 30, 2021 USD ($) property	Jun. 30, 2020 USD ($)
Concentration Risk [Line Items]
Number of Properties \| property	14
Gross Real Estate Assets	$ 225,500
Geographic Concentration Risk [Member]
Concentration Risk [Line Items]
Number of Properties \| property	14
Gross Real Estate Assets	$ 225,528
Percentage of Total Real Estate Assets	100.00%
Geographic Concentration Risk [Member] \| Rental Income [Member]
Concentration Risk [Line Items]
Revenues	$ 8,754	$ 7,791
Geographic Concentration Risk [Member] \| Maryland [Member]
Concentration Risk [Line Items]
Number of Properties \| property	6
Gross Real Estate Assets	$ 101,499
Percentage of Total Real Estate Assets	45.00%
Geographic Concentration Risk [Member] \| Maryland [Member] \| Rental Income [Member]
Concentration Risk [Line Items]
Revenues	$ 4,298	3,947
Geographic Concentration Risk [Member] \| Virginia [Member]
Concentration Risk [Line Items]
Number of Properties \| property	5
Gross Real Estate Assets	$ 82,726
Percentage of Total Real Estate Assets	36.70%
Geographic Concentration Risk [Member] \| Virginia [Member] \| Rental Income [Member]
Concentration Risk [Line Items]
Revenues	$ 2,688	2,394
Geographic Concentration Risk [Member] \| Pennsylvania [Member]
Concentration Risk [Line Items]
Number of Properties \| property	1
Gross Real Estate Assets	$ 26,811
Percentage of Total Real Estate Assets	11.90%
Geographic Concentration Risk [Member] \| Pennsylvania [Member] \| Rental Income [Member]
Concentration Risk [Line Items]
Revenues	$ 1,106	1,126
Geographic Concentration Risk [Member] \| Washington, D.C. [Member]
Concentration Risk [Line Items]
Number of Properties \| property	1
Gross Real Estate Assets	$ 8,393
Percentage of Total Real Estate Assets	3.70%
Geographic Concentration Risk [Member] \| Washington, D.C. [Member] \| Rental Income [Member]
Concentration Risk [Line Items]
Revenues	$ 325	$ 324
Geographic Concentration Risk [Member] \| Colorado [Member]
Concentration Risk [Line Items]
Number of Properties \| property	1
Gross Real Estate Assets	$ 6,099
Percentage of Total Real Estate Assets	2.70%
Geographic Concentration Risk [Member] \| Colorado [Member] \| Rental Income [Member]
Concentration Risk [Line Items]
Revenues	$ 337

Percentage of real estate property investment.

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The number of real estate properties owned as of the balance sheet date.

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Amount of real estate investment property which may include the following: (1) land available-for-sale; (2) land available-for-development; (3) investments in building and building improvements; (4) tenant allowances; (5) developments in-process; (6) rental properties; and (7) other real estate investments.

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