Summary Of Significant Accounting Policies (Narrative) (Details)	3 Months Ended
	Mar. 31, 2012
Summary Of Significant Accounting Policies [Line Items]
Date of establishment (year)	1948
Square footage of operating properties	74,100,000
Tenant Base [Member]
Summary Of Significant Accounting Policies [Line Items]
Percentage of rental revenue from largest tenant	3.40%