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		9 Months Ended	12 Months Ended
		Sep. 30, 2018	Dec. 31, 2017
Mortgage and notes payable		$ 1,862.1	$ 1,700.2
Kim Pru and Kim Pru II [Member]
Mortgage and notes payable		$ 621.8	$ 625.7
Weighted average interest rate		4.11%	3.59%
Weighted average remaining term (Month)	[1]	4 years 81 days	4 years 354 days
KIR [Member]
Mortgage and notes payable		$ 679.0	$ 702.0
Weighted average interest rate		4.40%	4.60%
Weighted average remaining term (Month)	[1]	3 years 213 days	3 years 345 days
CPP [Member]
Mortgage and notes payable		$ 84.4	$ 84.9
Weighted average interest rate		3.63%	2.91%
Weighted average remaining term (Month)	[1]	4 years 270 days	120 days
Other Joint Venture Programs [Member]
Mortgage and notes payable		$ 476.9	$ 287.6
Weighted average interest rate		4.18%	4.41%
Weighted average remaining term (Month)	[1]	6 years 279 days	2 years 96 days

[1] Includes extension options