Note 1 - Organization (Details Textual) $ / shares in Units, $ in Millions		12 Months Ended
	Feb. 09, 2017 USD ($) $ / shares shares	Dec. 31, 2019 USD ($) ft² a shares	Dec. 31, 2018 shares	Dec. 31, 2017 shares	Nov. 08, 2019	Oct. 27, 2017	May 09, 2017	Aug. 03, 2015
Formation Transaction, Units Converted to Commons Shares, Ratio								1
Percentage of Aggregate Cash Distributions From, and Profits and Losses		40.40%
Corporate Joint Venture [Member]
Joint Venture, Ownership Percentage		50.00%
Joint Venture, Committed Capital | $		$ 0.4
Corporate Joint Venture [Member] | General and Administrative Expense [Member]
Joint Venture Expense | $		$ 0.3
Residential Rental [Member] | Residential Property At 10 West 65th Street [Member]
Number of Units						82
Residential Rental [Member] | Property Located Brooklyn, New York [Member]
Number of Units					175
107 Columbia Heights in Brooklyn, NY [Member] | Apartment Building [Member]
Number of Units							158
Tribeca House properties in Manhattan [Member]
Number of Buildings		2
Tribeca House properties in Manhattan [Member] | Residential Rental [Member]
Gross Leasable Area		483,000
Tribeca House properties in Manhattan [Member] | Rental Retail and Parking [Member]
Gross Leasable Area		77,000
Tribeca House properties in Manhattan, Building One [Member]
Number of Stories		21
Tribeca House properties in Manhattan, Building Two [Member]
Number of Stories		12
Flatbush Gardens in Brooklyn [Member] | Multifamily [Member]
Number of Buildings		59
Number of Rentable Units		2,496
141 Livingston Street in Brooklyn [Member] | Office Building [Member]
Number of Stories		15
Gross Leasable Area		216,000
250 Livingston Street in Brooklyn [Member] | Office and Residential Building [Member]
Number of Stories		12
Gross Leasable Area | a		370,000
Aspen [Member]
Number of Stories		7
Aspen [Member] | Residential Rental [Member]
Gross Leasable Area		166,000
Aspen [Member] | Retail Site [Member]
Gross Leasable Area		21,000
Clover House [Member]
Number of Stories		11
Clover House [Member] | Apartment Building [Member]
Gross Leasable Area		102,000
Property at 10 W 65th St. Manhattan, NY [Member] | Residential Rental [Member]
Number of Stories		6
Gross Leasable Area		76,000
Residential Property in Brooklyn, NY [Member] | Residential Rental [Member]
Number of Stories		9
Property Located Brooklyn, New York [Member] | Residential Rental [Member]
Area of Real Estate Property		119,000
Common Stock [Member]
Stock Issued During Period, Shares, New Issues | shares		1,917		6,390,149
IPO [Member] | Common Stock [Member]
Stock Issued During Period, Shares, New Issues | shares	6,390,149
Shares Issued, Price Per Share | $ / shares	$ 13.50
Proceeds from Issuance Initial Public Offering | $	$ 79.0