Note 7 - Investment In and Advances to Real Estate Joint Ventures - Joint Venture Investments Accounted for Under the Equity Method, Debt Details (Details) - USD ($) $ in Millions		12 Months Ended
		Dec. 31, 2022	Dec. 31, 2021
Mortgage and notes payable		$ 1,383.4	$ 1,638.7
Prudential Investment Program [Member]
Mortgage and notes payable		$ 380.1	$ 426.9
Weighted average interest rate		5.20%	2.02%
Weighted average remaining term (Month)	[1]	33 months 3 days	45 months 18 days
KIR [Member]
Mortgage and notes payable		$ 297.9	$ 492.6
Weighted average interest rate		5.46%	2.55%
Weighted average remaining term (Month)	[1]	47 months 6 days	27 months 27 days
CPP [Member]
Mortgage and notes payable		$ 83.1	$ 84.2
Weighted average interest rate		6.14%	1.85%
Weighted average remaining term (Month)	[1]	43 months	55 months
Other Institutional Joint Ventures [Member]
Mortgage and notes payable		$ 233.5	$ 232.9
Weighted average interest rate		4.30%	1.65%
Weighted average remaining term (Month)	[1]	47 months 21 days	59 months 21 days
Other Joint Venture Programs [Member]
Mortgage and notes payable		$ 388.8	$ 402.1
Weighted average interest rate		4.10%	3.58%
Weighted average remaining term (Month)	[1]	71 months 24 days	83 months

[1] Average remaining term includes extensions