Note 4 - Investments In and Advances to Real Estate Joint Ventures (Details Textual) $ in Millions		6 Months Ended
		Jun. 30, 2021 USD ($) ft²	Dec. 31, 2020 ft²
Gross Leasable Area (Square Foot) | ft²	[1]	1,435
All Equity Method Investments [Member]
Number of Real Estate Properties		95	97
Gross Leasable Area (Square Foot) | ft²		20,900,000	21,200,000
Real Estate Joint Ventures [Member] | Operating Properties [Member]
Number of Real Estate Properties, Interest Disposed of or Transferred		2
Equity Method Investment, Sales Price | $		$ 53.7
Equity Method Investment, Realized Gain (Loss) on Disposal, Total | $		$ 4.2

[1] Gross leasable area ("GLA")