Note 3 - Real Estate - Disposition Activity (Details) - Disposition Activity Relating to Consolidated Operating Properties and Parcels [Member] $ in Millions	9 Months Ended
Sep. 30, 2020 USD ($)	Sep. 30, 2019 USD ($)
Aggregate sales price	$ 22.6	$ 163.8
Gain on sale of properties	$ 5.7	$ 47.4
Number of properties sold	3	12
Number of out-parcels sold	0	7
Number of land parcels sold	1	0

Amount after tax of gain (loss) not previously recognized resulting from the disposal of a discontinued operation.

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