Note 5 - Investments in and Advances to Real Estate Joint Ventures - Joint Venture Investments Accounted for Under the Equity Method, Debt Details (Details) - USD ($) $ in Millions		6 Months Ended	12 Months Ended
		Jun. 30, 2018	Dec. 31, 2017
Mortgage and notes payable		$ 1,881.1	$ 1,700.2
Kim Pru and Kim Pru II [Member]
Mortgage and notes payable		$ 623.1	$ 625.7
Weighted average interest rate		3.96%	3.59%
Weighted average remaining term (Month)	[1]	4 years 174 days	4 years 354 days
KIR [Member]
Mortgage and notes payable		$ 686.6	$ 702.0
Weighted average interest rate		4.63%	4.60%
Weighted average remaining term (Month)	[1]	3 years 174 days	3 years 345 days
CPP [Member]
Mortgage and notes payable		$ 84.3	$ 84.9
Weighted average interest rate		3.64%	2.91%
Weighted average remaining term (Month)	[1]	5 years 3 days	120 days
Other Joint Venture Programs [Member]
Mortgage and notes payable		$ 487.1	$ 287.6
Weighted average interest rate		4.18%	4.41%
Weighted average remaining term (Month)	[1]	6 years 324 days	2 years 96 days

[1] Includes extension options