Real Estate (Details) $ in Thousands	3 Months Ended		6 Months Ended
	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Jun. 30, 2015 USD ($)	Jun. 30, 2014 USD ($)	Dec. 31, 2014 USD ($)
Land	$ 6,374,779		$ 6,374,779		$ 6,295,404
Property, Plant and Equipment, Gross [Abstract]
Investment Building and Building Improvements	18,328,935		18,328,935		17,974,337
Fixtures and Equipment, Gross	1,446,235		1,446,235		1,365,276
Finite-Lived Intangible Asset, Acquired-in-Place Leases	515,154		515,154		511,891
Projects under development -CIP	1,240,244		1,240,244		1,343,919
Land Available for Development	127,559		127,559		184,556
Investment in real estate	28,032,906		28,032,906		27,675,383
Real Estate Investment Property, Accumulated Depreciation	(5,736,913)		(5,736,913)		(5,432,805)
Investment in real estate, net	22,295,993		22,295,993		22,242,578
Finite-Lived Intangible Assets, Gross	179,511		179,511		179,511
Amortization of Intangible Assets	(11,185)		(11,185)		(8,913)
Lease Intangible Assets, Net	168,326		168,326		170,598
Lease Intangible Liabilities	7,670		7,670		7,670
Amortization Of Intangible Liabilities	(2,839)		(2,839)		(2,258)
Lease Intangible Liabilities, net	$ 4,831		4,831		5,412
Amortization of above/below market leases			$ 1,691	$ 1,530
Weighted Average Ground Lease Amortization Period	49.8		49.8
Weighted Average Retail Lease Amortization Period	2.8		2.8
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	$ 1,692		$ 1,692
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
Retail Site [Member]
Property, Plant and Equipment, Gross [Abstract]
Amortization of above/below market leases	300	$ 300	500	600
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	(469)		(469)
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)
Assets [Member]
Property, Plant and Equipment, Gross [Abstract]
Below Market Lease, Gross	178,251		178,251		178,251
Finite-Lived Intangible Asset, Off-market Lease, Favorable, Gross	1,260		1,260		1,260
Liability [Member]
Property, Plant and Equipment, Gross [Abstract]
Below Market Lease, Gross	5,270		5,270		5,270
Off-market Lease, Unfavorable	2,400		2,400		2,400
Ground Lease [Member]
Property, Plant and Equipment, Gross [Abstract]
Amortization of above/below market leases	1,100	$ 1,100	2,200	$ 2,200
Finite-Lived Intangible Assets, Amortization Expense, Remainder of Fiscal Year	2,161		2,161
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
Projects under development [Member]
Property, Plant and Equipment, Gross [Abstract]
Projects under development - Land	406,251		406,251		466,764
Projects under development -CIP	833,993		833,993		877,155
Land held for development [Member]
Property, Plant and Equipment, Gross [Abstract]
Projects under development -CIP	30,172		30,172		39,190
Land Available for Development	$ 97,387		$ 97,387		$ 145,366