Acquired Intangible Assets And Liabilities (Summary Of Acquired Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	Mar. 31, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Acquired in place lease value, Net	$ 353,398	$ 335,381
Acquired above market leases, Net	27,595	29,701
Acquired below market leases, Net	108,270	85,819
Acquired In Place Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired in place lease, Gross amount	569,669	545,409
Accumulated amortization	(325,041)	(312,499)
Acquired in place lease value, Net	244,628	232,910
Acquired Above-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired above market leases, Gross amount	87,980	87,800
Accumulated amortization	(60,385)	(58,099)
Acquired above market leases, Net	27,595	29,701
Acquired Below-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired below market leases, Gross amount	228,490	201,275
Accumulated amortization	(120,220)	(115,456)
Acquired below market leases, Net	$ 108,270	$ 85,819