Summary Of Significant Accounting Policies (Variable Interest Entities) (Details) $ in Millions	Dec. 31, 2016 USD ($)	Jan. 01, 2016 USD ($)
Variable Interest Entity [Line Items]
Number of consolidated variable interest entities	14
Net real estate assets of consolidated VIEs	$ 1,017.7
Maximum exposure to loss in variable interest entity	439.1
Pike and Rose Hotel JV
Variable Interest Entity [Line Items]
Maximum exposure to loss in variable interest entity	$ 13.5	$ 13.5
Adjustments for New Accounting Pronouncement | Previous voting interest entity
Variable Interest Entity [Line Items]
Number of variable interest entities previously consolidated as voting interest entities		10
Net real estate assets of consolidated VIEs		$ 566.1