Acquired Intangible Assets And Liabilities (Narrative) (Details) (USD $) In Millions, unless otherwise specified	12 Months Ended
	Dec. 31, 2012	Dec. 31, 2011
Acquired Below-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Amortization of acquired above-market (below-market) lease	$ (10.3)	$ (7.9)
Expected remaining lives (years)	7 years 2 months 12 days
Acquired Above-Market Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Expected remaining lives (years)	5 years 3 months 18 days
Acquired In Place Lease Value [Member]
Finite-Lived Intangible Assets [Line Items]
Costs incurred to renew or extend leases	$ 54.0	$ 52.7
Expected remaining lives (years)	7 years 3 months 18 days
Weighted average period prior to renewal (years)	5 years 9 months 18 days