Note 5 - Investment in and Advances to Real Estate Joint Ventures - Joint Venture Investments Accounted for Under the Equity Method, Debt Details (Details) - USD ($) $ in Millions		3 Months Ended	12 Months Ended
		Mar. 31, 2019	Dec. 31, 2018
Mortgage and notes payable		$ 1,746.6	$ 1,782.6
Kim Pru and Kim Pru II [Member]
Mortgage and notes payable		$ 571.3	$ 572.6
Weighted average interest rate		4.28%	4.29%
Weighted average remaining term (Month)	[1]	3 years 300 days	4 years 30 days
KIR [Member]
Mortgage and notes payable		$ 638.2	$ 651.4
Weighted average interest rate		4.45%	4.43%
Weighted average remaining term (Month)	[1]	3 years 42 days	3 years 132 days
CPP [Member]
Mortgage and notes payable		$ 84.6	$ 84.4
Weighted average interest rate		4.04%	3.85%
Weighted average remaining term (Month)	[1]	4 years 93 days	4 years 180 days
Other Joint Venture Programs [Member]
Mortgage and notes payable		$ 452.5	$ 474.2
Weighted average interest rate		4.22%	4.26%
Weighted average remaining term (Month)	[1]	6 years 165 days	6 years 198 days

[1] Includes extension options