Real Estate (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2016	Mar. 31, 2015	Dec. 31, 2015
Land	$ 5,777,206		$ 5,864,046
Depreciable property:
Buildings and improvements	16,430,979		16,346,829
Furniture, fixtures and equipment	1,219,444		1,207,098
In-Place lease intangibles	465,392		483,160
Land Available for Development	154,023		158,843
Construction-in-progress	1,073,822		1,122,376
Investment in real estate	25,120,866		25,182,352
Accumulated depreciation	(4,977,274)		(4,905,406)
Investment in real estate, net	20,143,592		20,276,946
Lease intangible assets	179,511		179,511
Accumulated amortization	(14,582)		(13,451)
Lease intangible assets, net	164,929		166,060
Lease intangible liabilities	7,670		7,670
Accumulated amortization	(3,694)		(3,414)
Lease intangible liabilities, net	3,976		4,256
Amortization of above/below market leases	851	$ 846
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	2,574
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	3,781
Finite-Lived Intangible Assets, Amortization Expense, Year Two	4,250
Finite-Lived Intangible Assets, Amortization Expense, Year Three	4,250
Finite-Lived Intangible Assets, Amortization Expense, Year Four	4,250
Finite-Lived Intangible Assets, Amortization Expense, Year Five	4,254
Assets [Member]
Depreciable property:
Lease intangibles – below market	178,251		178,251
Retail lease intangibles – above market	1,260		1,260
Ground Lease [Member]
Depreciable property:
Amortization of above/below market leases	1,100	1,100
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	3,241
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	4,321
Finite-Lived Intangible Assets, Amortization Expense, Year Two	4,321
Finite-Lived Intangible Assets, Amortization Expense, Year Three	4,321
Finite-Lived Intangible Assets, Amortization Expense, Year Four	4,321
Finite-Lived Intangible Assets, Amortization Expense, Year Five	4,321
Retail Site [Member]
Depreciable property:
Amortization of above/below market leases	200	$ 200
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	(667)
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	(540)
Finite-Lived Intangible Assets, Amortization Expense, Year Two	(71)
Finite-Lived Intangible Assets, Amortization Expense, Year Three	(71)
Finite-Lived Intangible Assets, Amortization Expense, Year Four	(71)
Finite-Lived Intangible Assets, Amortization Expense, Year Five	(67)
Liability [Member]
Depreciable property:
Lease intangibles – below market	5,270		5,270
Ground lease intangibles – above market	2,400		2,400
Projects under development [Member]
Depreciable property:
Land	247,568		284,995
Construction-in-progress	826,254		837,381
Land held for development [Member]
Depreciable property:
Land Available for Development	114,149		120,007
Construction-in-progress	$ 39,874		$ 38,836