Note 2 - Real Estate (Details) - Components of Rental Property - USD ($) $ in Thousands		Dec. 31, 2015	Dec. 31, 2014
Property Subject to or Available for Operating Lease [Line Items]
Land		$ 2,728,257	$ 2,365,800
Buildings and improvements:
Buildings and improvements		8,661,362	7,520,095
Above market leases		155,451	121,774
In-place leases		509,435	399,293
Tenant relationships		19,104	20,858
		11,389,619	9,885,895
Accumulated depreciation and amortization (1)	[1]	(2,115,320)	(1,955,406)
Total		9,274,299	7,930,489
Land [Member]
Property Subject to or Available for Operating Lease [Line Items]
Land		2,660,722	2,291,338
Undeveloped Land [Member]
Property Subject to or Available for Operating Lease [Line Items]
Land		67,535	74,462
Buildings [Member]
Buildings and improvements:
Buildings and improvements		5,643,629	4,909,152
Building Improvements [Member]
Buildings and improvements:
Buildings and improvements		1,559,652	1,349,028
Tenant Improvements [Member]
Buildings and improvements:
Buildings and improvements		727,036	658,868
Fixtures And Leasehold Improvements [Member]
Buildings and improvements:
Buildings and improvements		$ 47,055	$ 61,122

[1] At December 31, 2015 and 2014, the Company had accumulated amortization relating to in-place leases, tenant relationships and above-market leases aggregating $357,581 and $290,748, respectively.