Acquired Intangible Assets And Liabilities (Summary Of Acquired Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2013	Dec. 31, 2012
Acquired In Place Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Gross amount	$ 722,434	$ 720,373
Accumulated amortization	(380,730)	(367,088)
Net	341,704	353,285
Acquired Above-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Gross amount	131,278	134,480
Accumulated amortization	(72,199)	(69,425)
Net	59,079	65,055
Acquired Below-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Gross amount	284,061	285,509
Accumulated amortization	(142,804)	(137,276)
Net	$ 141,257	$ 148,233