Note 3 - Operating Property Activities - Disposition Activity (Details) $ in Millions	3 Months Ended
Mar. 31, 2019 USD ($)	Mar. 31, 2018 USD ($)
Gain on sale of properties/change in control of interests	$ 23.6	$ 57.0
Disposition Activity Relating to Consolidated Operating Properties and Parcels [Member]
Aggregate sales price/gross fair value	74.2	522.5
Impairment charges	$ 1.0	$ 2.4
Number of operating properties sold/deconsolidated	5	20
Number of out-parcels sold	2	1

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

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