Note 5 - Dispositions of Real Estate - Disposition Activity (Details) $ in Millions	12 Months Ended
	Dec. 31, 2020 USD ($)	Dec. 31, 2019 USD ($)	[1]	Dec. 31, 2018 USD ($)
Gain on sale of properties/change in control of interests	$ 6.5	$ 79.2		$ 229.8
Disposition Activity Relating to Consolidated Operating Properties and Parcels [Member]
Aggregate sales price/gross fair value	$ 31.8	$ 344.7		$ 1,164.3
Number of operating properties sold/deconsolidated	3	20		54
Number of parcels sold	4	9		7

[1] Includes the land parcel sale at Dania Pointe, noted above in Footnote 4 of the Notes to Consolidated Financial Statements.