Note 5 - Investments In and Advances to Real Estate Joint Ventures (Details Textual) ft² in Thousands, $ in Millions		3 Months Ended
		Mar. 31, 2019 USD ($) ft²	Mar. 31, 2018 USD ($)	Dec. 31, 2018 ft²
Gross Leasable Area | ft²	[1]	125
All Equity Method Investments [Member]
Number of Real Estate Properties		105		109
Gross Leasable Area | ft²		22,800		23,200
Kim Pru and Kim Pru II [Member]
Number of Joint Ventures		4
Number Of Accounts		4
Kim Pru [Member]
Number of Joint Ventures		3
Real Estate Joint Ventures [Member] | Operating Properties [Member]
Number of Real Estate Properties, Interest Disposed of or Transferred		4	2
Equity Method Investment, Sales Price | $		$ 54.5	$ 17.1
Impairment of Long-Lived Assets to be Disposed of | $		$ 3.4	$ 2.1

[1] Gross leasable area ("GLA")