Note 4 - 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, 2022	Dec. 31, 2021
Mortgage and notes payable		$ 1,524.6	$ 1,638.7
Prudential Investment Program [Member]
Mortgage and notes payable		$ 381.8	$ 426.9
Weighted average interest rate		3.35%	2.02%
Weighted average remaining term (Month)	[1]	39 months 3 days	45 months 18 days
KIR [Member]
Mortgage and notes payable		$ 425.6	$ 492.6
Weighted average interest rate		2.88%	2.55%
Weighted average remaining term (Month)	[1]	38 months 24 days	27 months 27 days
CPP [Member]
Mortgage and notes payable		$ 83.6	$ 84.2
Weighted average interest rate		3.54%	1.85%
Weighted average remaining term (Month)	[1]	49 months 3 days	55 months
Other Institutional Joint Ventures [Member]
Mortgage and notes payable		$ 233.2	$ 232.9
Weighted average interest rate		3.34%	1.65%
Weighted average remaining term (Month)	[1]	53 months 24 days	59 months 21 days
Other Joint Venture Programs [Member]
Mortgage and notes payable		$ 400.4	$ 402.1
Weighted average interest rate		3.80%	3.58%
Weighted average remaining term (Month)	[1]	77 months 6 days	83 months

[1] Includes extension options