Note 4 - 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, 2023	Dec. 31, 2022
Mortgage and notes payable		$ 1,308.4	$ 1,383.4
Prudential Investment Program [Member]
Mortgage and notes payable		$ 342.3	$ 380.1
Weighted average interest rate		5.61%	5.20%
Weighted average remaining term (Month)	[1]	30 months 18 days	33 months 3 days
KIR [Member]
Mortgage and notes payable		$ 273.0	$ 297.9
Weighted average interest rate		5.82%	5.46%
Weighted average remaining term (Month)	[1]	48 months 6 days	47 months 6 days
CPP [Member]
Mortgage and notes payable		$ 82.8	$ 83.1
Weighted average interest rate		5.70%	6.14%
Weighted average remaining term (Month)	[1]	40 months 3 days	43 months
Other Institutional Joint Ventures [Member]
Mortgage and notes payable		$ 233.6	$ 233.5
Weighted average interest rate		5.76%	4.30%
Weighted average remaining term (Month)	[1]	44 months 21 days	47 months 21 days
Other Joint Venture Programs [Member]
Mortgage and notes payable		$ 376.7	$ 388.8
Weighted average interest rate		4.34%	4.10%
Weighted average remaining term (Month)	[1]	68 months	71 months 24 days

[1] Includes extension options