Acquired Intangible Assets And Liabilities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	3 Months Ended
	Mar. 31, 2013	Mar. 31, 2012
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired below-market lease value, net of acquired above-market lease value	$ 3.0	$ 2.2
Acquired Below-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Expected remaining lives	7 years
Acquired Above-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Expected remaining lives	5 years 2 months 12 days
Acquired In Place Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Costs incurred to renew or extend leases	$ 14.9	$ 12.0
Expected remaining lives	7 years 1 month 6 days
Weighted average period prior to renewal (years)	5 years 7 months 6 days