Note 5 - Investments In and Advances to Real Estate Joint Ventures - The Company's Share of Net Income/(Loss) (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Prudential Investment Program [Member]
Income of joint ventures, net	$ 1,900	$ 2,300	$ 7,200	$ 6,800
KIR [Member]
Income of joint ventures, net	9,400	8,200	27,200	22,900
CPP [Member]
Income of joint ventures, net	2,600	900	6,700	3,600
Other Institutional Joint Ventures [Member]
Income of joint ventures, net	900	0	900	0
Other Joint Venture Programs [Member]
Income of joint ventures, net	5,200	(200)	12,100	1,700
Joint Ventures [Member]
Income of joint ventures, net	$ 20,025	$ 11,233	$ 54,095	$ 35,039