Note 2 - Real Estate - Components of Rental Property (Details) - USD ($) $ in Thousands		Dec. 31, 2018	Dec. 31, 2017
land		$ 2,822,691	$ 3,019,284
Buildings and improvements:
Buildings and improvements		8,813,115	9,231,644
Real estate		11,635,806	12,250,928
Accumulated depreciation and amortization (1)	[1]	(2,385,287)	(2,433,053)
Real Estate Investment Property, Net, Total		9,250,519	9,817,875
Land [Member]
land		2,783,959	2,971,020
Undeveloped Land [Member]
land		38,732	48,264
Building [Member]
Buildings and improvements:
Buildings and improvements		5,697,269	6,047,413
Building Improvements [Member]
Buildings and improvements:
Buildings and improvements		1,696,440	1,653,581
Tenant Improvements [Member]
Buildings and improvements:
Buildings and improvements		730,623	753,501
Fixtures And Leasehold Improvements [Member]
Buildings and improvements:
Buildings and improvements		42,635	45,795
Above Market Leases [Member]
Buildings and improvements:
Buildings and improvements		133,913	153,484
In-place Leases and Tenant Relationships [Member]
Buildings and improvements:
Buildings and improvements		$ 512,235	$ 577,870

[1] At December 31, 2018 and 2017, the Company had accumulated amortization relating to in-place leases, tenant relationships and above-market leases aggregating $466,576 and $459,211, respectively.