Note 3 - Property Acquisitions, Developments and Other Investments - Previous Ownership Interest and Gain on Change of Interest (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015
Gain on change in control of interests, net	$ 57.4	$ 149.2
Oakwood Plaza North [Member]
Previous ownership interest	55.00%
Gain on change in control of interests, net	$ 46.5
Elmont Plaza [Member]
Previous ownership interest		50.00%
Gain on change in control of interests, net		$ (0.2)
Gateway Plaza [Member]
Previous ownership interest	15.00%
Gain on change in control of interests, net
Kimstone [Member]
Previous ownership interest		33.30%
Gain on change in control of interests, net		$ 140.0
GEPT Portfolio [Member]
Previous ownership interest	15.00%
Gain on change in control of interests, net	$ 6.6
Montgomery Plaza [Member]
Previous ownership interest		20.00%
Gain on change in control of interests, net		$ 6.3
Kim Pru [Member]
Previous ownership interest	15.00%
Gain on change in control of interests, net	$ 0.8
Conroe Marketplace [Member]
Previous ownership interest		15.00%
Gain on change in control of interests, net		$ 2.4
Hamden Mart [Member]
Previous ownership interest	47.95%
Gain on change in control of interests, net	$ 3.5
Shops at District Heights [Member]
Previous ownership interest		15.00%
Gain on change in control of interests, net		$ 0.7