Note 6 - Mortgage and Other Indebtedness - (Details Textual)						1 Months Ended						3 Months Ended				9 Months Ended			12 Months Ended
		Jun. 04, 2021 USD ($)	May 21, 2021 USD ($)	Jun. 16, 2020 USD ($) Capital	Dec. 27, 2019 USD ($) Derivative	Jul. 31, 2021	Mar. 31, 2021 USD ($)	Dec. 31, 2020 USD ($)		Jun. 30, 2020 USD ($)	Dec. 31, 2019 USD ($) Subsidiary	Sep. 30, 2021 USD ($)		Jun. 30, 2021 USD ($)	Sep. 30, 2020 USD ($)	Sep. 30, 2021 USD ($)		Sep. 30, 2020 USD ($)	Dec. 31, 2020 USD ($)		Mar. 31, 2022	Dec. 31, 2021	Oct. 06, 2021 USD ($)	Oct. 01, 2021 USD ($)	Mar. 18, 2021 USD ($)	Apr. 20, 2020 USD ($)
Debt Instrument [Line Items]
Long-term debt outstanding												$ 159,441,000				$ 159,441,000
Repayments of debt																12,734,000		$ 3,087,000
Interest expense												2,387,000			$ 1,722,000	7,346,000		4,913,000
Balance outstanding												159,441,000				159,441,000
Principal balance of mortgage loan								$ 122,060,000				157,361,000				157,361,000			$ 122,060,000
Deferred financing costs, gross								1,400,000				1,900,000				1,900,000			1,400,000
Deferred financing costs, net								900,000				1,000,000.0				1,000,000.0			900,000
Debt discounts, gross								1,400,000				2,000,000.0				2,000,000.0			1,400,000
Debt instrument net of discount								$ 900,000				$ 1,100,000				1,100,000			$ 900,000
Income (expenses) related to fair value adjustments on derivatives																$ 300,000		(700,000)
MVB Revolver [Member]
Debt Instrument [Line Items]
Maturity date																Dec. 27, 2021			Dec. 27, 2021
Interest Rate	[1]							6.75%				6.75%				6.75%			6.75%
Mortgages [Member]
Debt Instrument [Line Items]
Outstanding mortgage indebtedness																$ 71,800,000			$ 38,100,000
Mortgage Loan [Member]
Debt Instrument [Line Items]
Mortgage loan maturity period																2028-10
PPP Loan [Member]
Debt Instrument [Line Items]
Unsecured loan																										$ 800,000
Second PPP Loan [Member]
Debt Instrument [Line Items]
Unsecured loan																									$ 800,000
Subsequent Event [Member] | Mortgage Loan [Member]
Debt Instrument [Line Items]
Mortgage loan secured by the property																							$ 23,500,000
Sub-OP [Member]
Debt Instrument [Line Items]
Number of additional capital contribution from preferred investor | Capital				2
Preferred investor, additional capital contribution				$ 2,900,000						$ 2,900,000
Proceeds from refinance to repayment				750,000
Preferred investor, additional available capital contribution				300,000
Sub-OP [Member] | Subsequent Event [Member]
Debt Instrument [Line Items]
Preferred investor, additional available capital contribution																								$ 1,000,000.0
Preferred units remaining contributed capital																								$ 0
LIBOR [Member]
Debt Instrument [Line Items]
Debt instrument variable rate																0.08%
Prime Rate [Member] | MVB Revolver [Member]
Debt Instrument [Line Items]
Debt instrument variable rate																1.50%
Prime Rate [Member] | Subsequent Event [Member] | Mortgage Loan [Member]
Debt Instrument [Line Items]
Interest Rate																							0.35%
Interest Rate Swap [Member]
Debt Instrument [Line Items]
Fair value of interest rate swap liability								$ 700,000				$ 500,000				$ 500,000			700,000
Interest Rate Swap [Member] | Accounts Payable and Accrued Expenses [Member]
Debt Instrument [Line Items]
Fair value of interest rate swap liability								700,000				500,000				500,000			700,000
Interest Rate Swap [Member] | Subsequent Event [Member] | Mortgage Loan [Member]
Debt Instrument [Line Items]
Interest Rate																							4.082%
Maximum [Member]
Debt Instrument [Line Items]
Deferred financing costs, amortization expense												400,000			200,000	900,000		$ 700,000
Income (expenses) related to fair value adjustments on derivatives												100,000			$ 100,000
Maximum [Member] | Interest Rate Cap [Member]
Debt Instrument [Line Items]
Fair value of interest rate cap assets								100,000				100,000				100,000			100,000
Maximum [Member] | Interest Rate Cap [Member] | Other Assets, Net [Member]
Debt Instrument [Line Items]
Fair value of interest rate cap assets								$ 100,000				$ 100,000				$ 100,000			$ 100,000
Basis Term Loan [Member]
Debt Instrument [Line Items]
Number of subsidiaries as borrowers entered in loan agreement | Subsidiary											6
Maturity date											Jan. 01, 2023					Jan. 01, 2023			Jan. 01, 2023
Maturity date description																The Basis Term Loan matures on January 1, 2023, subject to two one-year extension options, subject to certain conditions.
Interest Rate								6.125%	[1]		6.125%	6.125%	[1]			6.125%	[1]		6.125%	[1]
Long-term debt outstanding												$ 66,900,000				$ 66,900,000
Balance outstanding												66,900,000				66,900,000
Debt instrument net of discount								$ 745,000				$ 466,000				$ 466,000			$ 745,000
Basis Term Loan [Member] | Sub-OP [Member]
Debt Instrument [Line Items]
Preferred investor, additional capital contribution				2,400,000
Basis Term Loan [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Debt instrument variable rate											3.85%					3.85%
Basis Term Loan [Member] | Interest Rate Cap [Member]
Debt Instrument [Line Items]
Long-term debt amount					$ 66,900,000
Debt instrument variable rate					6.125%
Basis Term Loan [Member] | Interest Rate Cap [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Debt instrument variable rate					3.85%											3.50%
Derivative variable rate											3.50%
Debt instrument, effective interest rate					3.50%
Basis Term Loan [Member] | Maximum [Member]
Debt Instrument [Line Items]
Long-term debt amount											$ 66,900,000
Basis Preferred Interest [Member]
Debt Instrument [Line Items]
Maturity date	[2],[3]															Jan. 01, 2023			Jan. 01, 2023
Interest Rate	[1],[3],[4]							14.00%				14.00%				14.00%			14.00%
Debt instrument net of discount								$ 150,000				$ 94,000				$ 94,000			$ 150,000
Basis Preferred Interest [Member] | Sub-OP [Member]
Debt Instrument [Line Items]
Preferred investor investment commitment amount											$ 10,700,000
Preferred investor, capital contribution																$ 6,900,000
Annual return percentage on initial capital contribution											14.00%
Interest percentage on excess of commitment amount											20.00%
Description on extended redemption date																December 31, 2023 and December 31, 2024
Payment fee percentage, first extension option											0.25%
Payment fee percentage, second extension option											0.50%
Preferred Investor payments, description																Additionally, at the Redemption Date, the Preferred Investor is entitled to an amount equal to (a) the product of (i) the aggregate amount of capital contributions made and (ii) 0.4, less (b) the aggregate amount of Class A return payments made to the Preferred Investor (the “Minimum Multiple Amount”).
Basis Preferred Interest [Member] | Sub-OP [Member] | Class A Units [Member]
Debt Instrument [Line Items]
Interest percentage in exchange of capital contribution																1.00%
Basis Preferred Interest [Member] | Maximum [Member]
Debt Instrument [Line Items]
Preferred investor investment commitment amount											$ 10,700,000
Basis Preferred Interest Minimum Multiple Amount [Member]
Debt Instrument [Line Items]
Long-term debt outstanding								1,800,000				1,000,000.0				$ 1,000,000.0			1,800,000
Balance outstanding								$ 1,800,000				1,000,000.0				1,000,000.0			$ 1,800,000
Basis Preferred Interest Minimum Multiple Amount [Member] | Sub-OP [Member]
Debt Instrument [Line Items]
Long-term debt outstanding												1,000,000.0				1,000,000.0
Balance outstanding												$ 1,000,000.0				1,000,000.0
Other Capital Contribution [Member] | Sub-OP [Member]
Debt Instrument [Line Items]
Preferred investor, additional capital contribution				$ 500,000
Preferred units, cumulative annual return				13.00%						13.00%
MVB Loan Agreement [Member]
Debt Instrument [Line Items]
Long-term debt outstanding											6,500,000
Loan agreement deposit requirement																$ 3,000,000.0
Loan agreement deposit requirement default interest charges percentage																1.00%
Balance outstanding											$ 6,500,000
MVB Loan Agreement [Member] | MVB Revolver [Member]
Debt Instrument [Line Items]
Maturity date							Dec. 27, 2022	Dec. 27, 2021			Dec. 27, 2020					Dec. 27, 2022
Interest Rate												6.75%				6.75%
Long-term debt outstanding											$ 2,000,000.0
Line of credit facility, periodic payment required							$ 250,000	$ 250,000
Repayments of debt							$ 250,000
Line of credit facility, payments term							10 years	10 years
Balance outstanding											$ 2,000,000.0
MVB Loan Agreement [Member] | MVB Term Loan [Member]
Debt Instrument [Line Items]
Maturity date											Dec. 27, 2022
Interest Rate											6.75%
Long-term debt outstanding											$ 4,500,000
Balance outstanding											$ 4,500,000
MVB Loan Agreement [Member] | MVB Term Loan [Member] | MVB Revolver [Member]
Debt Instrument [Line Items]
Debt instrument additional borrowing available												$ 0				$ 0
MVB Loan Agreement [Member] | Prime Rate [Member] | MVB Revolver [Member]
Debt Instrument [Line Items]
Debt instrument variable rate											1.50%
MVB Loan Agreement [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.30%				1.30%
MVB Loan Agreement [Member] | Maximum [Member] | MVB Revolver [Member]
Debt Instrument [Line Items]
Debt service coverage ratio								1.00%											1.00%
MVB Loan Agreement [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.00%				1.00%
Consolidated funded debt ratio																8.00%
Funds available under other lines of credit																$ 5,000,000.0
MVB Loan Agreement [Member] | Minimum [Member] | MVB Revolver [Member]
Debt Instrument [Line Items]
Debt service coverage ratio								1.00%											1.00%
Funds available under other lines of credit								$ 3,000,000.0
Lamont Street Preferred Interest [Member]
Debt Instrument [Line Items]
Long-term debt outstanding												$ 800,000				$ 800,000
Description on extended redemption date																September 30, 2024 and September 30, 2025
Payment fee percentage, first extension option																0.25%
Payment fee percentage, second extension option																0.50%
Preferred Investor payments, description																Additionally, at the Lamont Street Redemption Date, Lamont Street is entitled to (i) a redemption fee of 0.50% of the capital contributions returned and (ii) an amount equal to (a) the product of (i) the aggregate amount of capital contributions made and (ii) 0.26, less (b) the aggregate amount of Lamont Street Class A Return payments made to Lamont Street (the “Lamont Street Minimum Multiple Amount”).
Percentage of redemption fee of capital contribution returned																0.50%
Interest expense														$ 1,000,000.0
Balance outstanding												$ 800,000				$ 800,000
Lamont Street Preferred Interest [Member] | Class A Units [Member]
Debt Instrument [Line Items]
Annual return percentage on initial capital contribution																13.50%
Cumulative annual return percentage, paid current																10.00%
Cumulative annual return percentage, accrued																3.50%
Lamont Street Preferred Interest [Member] | Class A Units [Member] | Highlandtown [Member]
Debt Instrument [Line Items]
Preferred investor, capital contribution			$ 3,900,000
Interest percentage in exchange of capital contribution			1.00%
Lamont Street Preferred Interest [Member] | Class A Units [Member] | Spotswood [Member]
Debt Instrument [Line Items]
Preferred investor, capital contribution		$ 3,900,000
Interest percentage in exchange of capital contribution		1.00%
Lamont Street Preferred Interest [Member] | Minimum [Member] | Highlandtown [Member]
Debt Instrument [Line Items]
Preferred investor approval rights, Minimum amount of capital expenditure to be incurred																$ 100,000
Lamont Street Preferred Interest [Member] | Minimum [Member] | Spotswood [Member]
Debt Instrument [Line Items]
Preferred investor approval rights, Minimum amount of capital expenditure to be incurred																$ 100,000
Hollinswood Mortgage [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.40%				1.40%
Hollinswood Mortgage [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.00%				1.00%
Vista Mortgage [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.50%				1.50%
Vista Mortgage [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.00%				1.00%
Brookhill Mortgage [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.35%				1.35%
Brookhill Mortgage [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.00%				1.00%
Highlandtown Mortgage [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.30%				1.30%
Highlandtown Mortgage [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.00%				1.00%
Cromwell Mortgage [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.00%				1.00%
Cromwell Mortgage [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.00%				1.00%
Spotswood Mortgage [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.15%				1.15%
Spotswood Mortgage [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.00%				1.00%
Vista Shops at Golden Mile Loan [Member]
Debt Instrument [Line Items]
Maturity date	[5]															Jun. 24, 2023			Jun. 24, 2023
Interest Rate							3.83%	3.83%	[1],[5]			3.83%	[1],[5]			3.83%	[1],[5]		3.83%	[1],[5]
Mortgage loan maturity period							2023-06
Principal balance of mortgage loan							$ 11,700,000
Payment of basis preferred interest							$ 1,900,000
Payment of accrued interest														46,000
Payment to escrow account														1,100,000
Debt instrument net of discount								$ 0				$ 45,000				$ 45,000			$ 0
Vista Shops at Golden Mile Loan [Member] | Mortgage Loan [Member]
Debt Instrument [Line Items]
Maturity date																Jan. 25, 2021
Vista Shops at Golden Mile Loan [Member] | Sub-OP [Member]
Debt Instrument [Line Items]
Payment of basis preferred interest														$ 750,000
Vista Shops at Golden Mile Loan [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Debt instrument variable rate																2.50%
Lamar Station Plaza East [Member]
Debt Instrument [Line Items]
Maturity date						Jul. 31, 2022
Lamar Station Plaza East [Member] | Maximum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.05%				1.05%
Lamar Station Plaza East [Member] | Maximum [Member] | Forecast
Debt Instrument [Line Items]
Debt service coverage ratio																					1.25%	1.15%
Lamar Station Plaza East [Member] | Minimum [Member]
Debt Instrument [Line Items]
Debt service coverage ratio												1.00%				1.00%
Lamar Station Plaza East [Member] | Minimum [Member] | Forecast
Debt Instrument [Line Items]
Debt service coverage ratio																					1.00%	1.00%
Hollinswood Loan [Member]
Debt Instrument [Line Items]
Maturity date																Dec. 01, 2024			Dec. 01, 2024
Interest Rate	[1]							4.06%				4.06%				4.06%			4.06%
Hollinswood Loan [Member] | LIBOR [Member]
Debt Instrument [Line Items]
Debt instrument variable rate																2.25%			2.25%
Hollinswood Loan [Member] | Interest Rate Cap [Member]
Debt Instrument [Line Items]
Debt instrument variable rate					4.06%
Hollinswood Loan [Member] | Interest Rate Swap [Member]
Debt Instrument [Line Items]
Long-term debt outstanding					$ 10,200,000
Debt instrument additional borrowing available					3,000,000.0
Balance outstanding					$ 10,200,000
Number of derivatives held | Derivative					2

[1] For floating rate loans tied to LIBOR, based on the one-month LIBOR rate of 0.08%, as of September 30, 2021.

[2] If the Basis Term Loan is paid in full earlier than its maturity date, the Basis Preferred Interest in the Sub-OP (as defined below) will mature at that time.

[3] The outstanding balance includes approximately $1.0 million and $1.8 million of indebtedness as of September 30, 2021 and December 31, 2020, respectively, related to the Multiple Minimum Amount owed to the Preferred Investor as described below under the heading “—Basis Preferred Interest”.

[4] In June 2020, the Preferred Investor made additional capital contributions of approximately $2.9 million as described below under the heading “—Basis Preferred Interest” of which approximately $1.9 million was outstanding at September 30, 2021. The Preferred Investor is entitled to a cumulative annual return of 13.0% on the additional contributions.

[5] The Company completed the refinance of this loan in March 2021 as described below under the heading “—Mortgage Indebtedness”. The prior loan matured on January 25, 2021 and carried an interest rate of LIBOR plus 2.5% per annum.