Real Estate (Details) - USD ($) $ in Thousands	3 Months Ended		9 Months Ended
	Sep. 30, 2015	Sep. 30, 2014	Sep. 30, 2015	Sep. 30, 2014	Dec. 31, 2014
Land	$ 6,424,887		$ 6,424,887		$ 6,295,404
Depreciable property:
Buildings and improvements	18,527,779		18,527,779		17,974,337
Furniture, fixtures and equipment	1,497,314		1,497,314		1,365,276
In-Place lease intangibles	515,154		515,154		511,891
Construction-in-progress	1,039,657		1,039,657		1,343,919
Land Available for Development	154,690		154,690		184,556
Investment in real estate	28,159,481		28,159,481		27,675,383
Accumulated depreciation	(5,914,695)		(5,914,695)		(5,432,805)
Investment in real estate, net	22,244,786		22,244,786		22,242,578
Lease intangible assets	179,511		179,511		179,511
Accumulated amortization	(12,318)		(12,318)		(8,913)
Lease intangible assets, net	167,193		167,193		170,598
Lease intangible liabilities	7,670		7,670		7,670
Accumulated amortization	(3,129)		(3,129)		(2,258)
Lease intangible liabilities, net	4,541		4,541		5,412
Amortization of above/below market leases			2,534	$ 2,376
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	848		848
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	3,425		3,425
Finite-Lived Intangible Assets, Amortization Expense, Year Two	3,781		3,781
Finite-Lived Intangible Assets, Amortization Expense, Year Three	4,250		4,250
Finite-Lived Intangible Assets, Amortization Expense, Year Four	4,250		4,250
Finite-Lived Intangible Assets, Amortization Expense, Year Five	4,250		4,250
Projects under development [Member]
Depreciable property:
Land	295,798		295,798		466,764
Construction-in-progress	743,859		743,859		877,155
Land held for development [Member]
Depreciable property:
Construction-in-progress	34,683		34,683		39,190
Land Available for Development	120,007		120,007		145,366
Joint Venture Partner [Member]
Depreciable property:
Investment in real estate, net	116,700		116,700
Assets [Member]
Depreciable property:
Lease intangibles – below market	178,251		178,251		178,251
Retail lease intangibles – above market	1,260		1,260		1,260
Ground Lease [Member]
Depreciable property:
Amortization of above/below market leases	1,000	$ 1,000	3,200	3,200
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	1,080		1,080
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	4,321		4,321
Finite-Lived Intangible Assets, Amortization Expense, Year Two	4,321		4,321
Finite-Lived Intangible Assets, Amortization Expense, Year Three	4,321		4,321
Finite-Lived Intangible Assets, Amortization Expense, Year Four	4,321		4,321
Finite-Lived Intangible Assets, Amortization Expense, Year Five	4,321		4,321
Retail Site [Member]
Depreciable property:
Amortization of above/below market leases	200	$ 300	700	$ 900
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	(232)		(232)
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	(896)		(896)
Finite-Lived Intangible Assets, Amortization Expense, Year Two	(540)		(540)
Finite-Lived Intangible Assets, Amortization Expense, Year Three	(71)		(71)
Finite-Lived Intangible Assets, Amortization Expense, Year Four	(71)		(71)
Finite-Lived Intangible Assets, Amortization Expense, Year Five	(71)		(71)
Liability [Member]
Depreciable property:
Lease intangibles – below market	5,270		5,270		5,270
Ground lease intangibles – above market	$ 2,400		$ 2,400		$ 2,400