Summary of Significant Accounting Policies Deferred Leasing and Other Costs (Details) - USD ($) $ in Thousands	12 Months Ended
	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Deferred Leasing and Other [Abstract]
Amortization of Intangible Assets	$ 33,700	$ 38,700	$ 55,400
Deferred Costs, Leasing, Gross	323,534	302,282
Finite-Lived Intangible Asset, Acquired-in-Place Leases	268,978	289,518
Deferred Leasing Costs and Finite Lived Intangible Assets Acquired, gross	592,512	591,800
Deferred Costs, Leasing, Accumulated Amortization	(108,227)	(106,912)
Finite-Lived Intangible Assets, Accumulated Amortization	(142,022)	(138,514)
Deferred Costs, Leasing, Net	342,263	346,374
Finite-Lived Intangible Assets, Amortization Expense, Next Twelve Months	32,381
Finite-Lived Intangible Assets, Amortization Expense, Year Two	24,532
Finite-Lived Intangible Assets, Amortization Expense, Year Three	18,452
Net Charge to Rental Income Third Year	718
Finite-Lived Intangible Assets, Amortization Expense, Year Four	12,977
Finite-Lived Intangible Assets, Amortization Expense, Year Five	8,210
Finite-Lived Intangible Assets, Amortization Expense, after Year Five	26,148
Finite-Lived Intangible Assets, Net	122,700
Net Charge to Rental Income Year One	987
Net Charge to Rental Income Year Two	755
Net Charge to Rental Income Year Four	640
Net Charge to Rental Income Year Five	368
Net Charge to Rental Income After Year Five	788
Net Charge to Rental Income	4,256
Amortization of above market lease, charge to rental income	$ 1,000	$ 1,600	$ 2,200