Note 4 - 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, 2020	Sep. 30, 2019	Sep. 30, 2020	Sep. 30, 2019
Prudential Investment Program [Member]
Income of joint ventures, net	$ 2,300	$ 5,600	$ 6,800	$ 11,300
KIR [Member]
Income of joint ventures, net	8,200	8,800	22,900	40,600
CPP [Member]
Income of joint ventures, net	900	1,100	3,600	4,200
Other Joint Venture Programs [Member]
Income of joint ventures, net	(200)	2,200	1,700	2,900
Joint Ventures [Member]
Income of joint ventures, net	$ 11,233	$ 17,673	$ 35,039	$ 58,960