Acquired Intangible Assets And Liabilities (Summary Of Acquired Intangible Assets) (Details) (USD $) In Thousands, unless otherwise specified	Sep. 30, 2012	Dec. 31, 2011
Finite-Lived Intangible Assets [Line Items]
Acquired in place lease value, Net	$ 492,393	$ 335,381
Acquired above market leases, Net	68,269	29,701
Acquired below market leases, Net	152,876	85,819
Acquired In Place Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired in place lease, Gross amount	708,968	545,409
Accumulated amortization	(351,596)	(312,499)
Acquired in place lease value, Net	357,372	232,910
Acquired Above-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired above market leases, Gross amount	134,079	87,800
Accumulated amortization	(65,810)	(58,099)
Acquired above market leases, Net	68,269	29,701
Acquired Below-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired below market leases, Gross amount	283,543	201,275
Accumulated amortization	(130,667)	(115,456)
Acquired below market leases, Net	$ 152,876	$ 85,819