Note 3 - Property Acquisitions, Developments and Other Investments - Pro Forma Information (Details) - USD ($) $ / shares in Units, $ in Millions	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Revenues from rental properties	$ 1,174.9	$ 1,198.6	$ 1,097.8
Net income	397.7	921.6	521.9
Net income available to the Company	$ 344.2	$ 852.6	$ 451.7
Basic (in dollars per share)	$ 0.82	$ 2.07	$ 1.10
Diluted (in dollars per share)	$ 0.82	$ 2.07	$ 1.10