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, 2019	Sep. 30, 2018	Sep. 30, 2019	Sep. 30, 2018
Prudential Investment Program [Member]
Income of joint ventures, net		$ 5,600	$ 3,000	$ 11,300	$ 8,500
KIR [Member]
Income of joint ventures, net		8,800	8,000	40,600	26,900
CPP [Member]
Income of joint ventures, net		1,100	1,200	4,200	3,700
Other Joint Venture Programs [Member]
Income of joint ventures, net	[1]	2,200	4,300	2,900	13,400
Joint Ventures [Member]
Income of joint ventures, net		$ 17,673	$ 16,533	$ 58,960	$ 52,486

[1] During the nine months ended September 30, 2018, a joint venture investment distributed cash proceeds resulting from the refinancing of an existing loan of which the Company's share was $3.6 million. The distribution was in excess of the Company's carrying basis in this joint venture investment and as such was recognized as income.