Note 6 - Investments 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, 2023	Dec. 31, 2022
Mortgage and notes payable		$ 1,248.9	$ 1,383.4
Prudential Investment Program [Member]
Mortgage and notes payable		$ 291.6	$ 380.1
Weighted average interest rate		6.00%	5.20%
Weighted average remaining term (Month)	[1]	24 months 18 days	33 months 3 days
KIR [Member]
Mortgage and notes payable		$ 273.4	$ 297.9
Weighted average interest rate		5.82%	5.46%
Weighted average remaining term (Month)	[1]	39 months 6 days	47 months 6 days
CPP [Member]
Mortgage and notes payable		$ 81.9	$ 83.1
Weighted average interest rate		5.12%	6.14%
Weighted average remaining term (Month)	[1]	31 months	43 months
Other Institutional Joint Ventures [Member]
Mortgage and notes payable		$ 234.1	$ 233.5
Weighted average interest rate		5.76%	4.30%
Weighted average remaining term (Month)	[1]	35 months 21 days	47 months 21 days
Other Joint Venture Programs [Member]
Mortgage and notes payable		$ 367.9	$ 388.8
Weighted average interest rate		4.44%	4.10%
Weighted average remaining term (Month)	[1]	59 months 18 days	71 months 24 days

[1] Average remaining term includes extensions