Summary Of Significant Accounting Policies (Narrative) (Details)	9 Months Ended
	Sep. 30, 2012 segment foreign sqft
Summary Of Significant Accounting Policies [Line Items]
Date of establishment (year)	1948
Square footage of operating properties	59,800,000
Number of Foreign Operations	0
Number of Reportable Segments	1
Tenant Base [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	3.30%
Revenues, Segment [Member]
Summary Of Significant Accounting Policies [Line Items]
Concentration risk percentage	10.00%