Note 3 - Property Acquisitions, Developments and Other Investments (Details Textual) ft² in Millions		12 Months Ended
	Sep. 20, 2017 USD ($) ft²	Dec. 31, 2018 USD ($)	Dec. 31, 2017 USD ($)	Dec. 31, 2016 USD ($)
Payments to Acquire Real Estate, Total		$ 5,407,000	$ 153,854,000	$ 203,190,000
Proceeds from Delayed Tax Exempt Exchange			$ 162,400,000
Business Acquisition, Percentage of Voting Interests Acquired			54.27%
Real Estate Revenue From Acquisitions During Period		0	$ 31,000,000	23,800,000
Proceeds from Insurance Settlement, Investing Activities		$ 16,222,000
PUERTO RICO
Number of Real Estate Properties	7	7
Area of Real Estate Property | ft²	2.2
Property Insurance, Coverage	$ 62,000,000
Business Interruption Insurance, Coverage	39,300,000
Insurance, Deductible	$ 1,200,000
PUERTO RICO | Hurricane [Member]
Estimated Insurance Recoveries		$ 30,300,000
Proceeds from Insurance Settlement, Investing Activities		20,200,000	4,200,000
Real Estate Investment Properties, Write-offs			16,000,000
Proceeds from Insurance Settlement, Operating Activities		$ 2,800,000	$ 1,600,000
Land Parcels Adjacent to Shopping Center Located in Ardmore, PA and Elmont, NY [Member]
Number of Land Parcels Acquired		2
Payments to Acquire Real Estate, Total		$ 5,400,000