Note 9 - Variable Interest Entities ("VIE") (Details Textual) $ in Thousands		12 Months Ended
		Dec. 31, 2019 USD ($)	Dec. 31, 2018 USD ($)
Variable Interest Entity, Number of Entities		23	24
Assets, Total	[1]	$ 10,997,867	$ 10,999,100
Liabilities, Total	[2]	$ 6,051,017	$ 5,564,365
Consolidated Operating Properties [Member]
Variable Interest Entity, Number of Entities		22	23
Consolidated Operating Properties [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets, Total		$ 900,000	$ 1,100,000
Liabilities, Total		70,900	$ 75,200
Real Estate Under Development [Member]
Variable Interest Entity, Number of Entities			1
Variable Interest Entity, Financial or Other Support, Amount		40,000
Real Estate Under Development [Member] | Variable Interest Entity, Primary Beneficiary [Member]
Assets, Total		346,900	$ 275,600
Liabilities, Total		$ 82,500	$ 68,000

[1] Includes restricted assets of consolidated variable interest entities ("VIEs") at December 31, 2019 and December 31, 2018 of $245,489 and $239,012, respectively. See Footnote 9 of the Notes to Consolidated Financial Statements.

[2] Includes non-recourse liabilities of consolidated VIEs at December 31, 2019 and December 31, 2018 of $153,436 and $143,186, respectively. See Footnote 9 of the Notes to Consolidated Financial Statements.