Summary of Significant Accounting Policies (Narrative) (Details) (USD $)	12 Months Ended
	Dec. 31, 2013 properties segment	Dec. 31, 2012	Dec. 31, 2011	Dec. 31, 2013 Building and Building Improvements [Member] Minimum [Member]	Dec. 31, 2013 Building and Building Improvements [Member] Maximum [Member]	Dec. 31, 2013 Minor Improvements, Furniture and Equipment [Member] Minimum [Member]	Dec. 31, 2013 Minor Improvements, Furniture and Equipment [Member] Maximum [Member]	Dec. 31, 2013 Plaza El Segundo [Member]	Dec. 31, 2012 Plaza El Segundo [Member]	Dec. 30, 2011 Plaza El Segundo [Member]	Dec. 31, 2013 Melville Mall [Member]	Dec. 31, 2012 Melville Mall [Member]	Oct. 16, 2006 Melville Mall [Member] year	Oct. 16, 2021 Melville Mall [Member] Purchased Call Option [Member]	Oct. 16, 2023 Melville Mall [Member] Put Option [Member]
Summary of Significant Accounting Policies [Line Items]
Dividends Reinvested in Noncash Financing Transaction	$ 1,779,000	$ 1,864,000	$ 1,941,000
Property, Plant and Equipment, Useful Life				35 years	50 years	2 years	20 years
Allowance for Doubtful Accounts Receivable	12,700,000	15,900,000
Straight Line Rents, Collection Of Accounts Receivable, Period	1 year
Deferred Rent Receivables, Net	60,600,000	56,100,000
Depreciation Expense Real Estate	147,700,000	128,700,000	114,200,000
Investments Classified As Cash And Cash Equivalents, Initial Maturity	3 months
Cash, Uninsured Amount	85,200,000
Interest Rate Cash Flow Hedge Gain (Loss) to be Reclassified During Next 12 Months, Net	4,100,000
Residual Profit Maxiumum	50.00%
Master Lease Term													20
Secured Debt F R T													34,200,000
Purchase Price Under Option														5,000,000	5,000,000
Mortgages payable	588,456,000	760,789,000						182,100,000	183,900,000		20,700,000	21,400,000
Real estate, net	3,798,992,000	3,555,379,000						183,400,000	189,400,000		62,600,000	63,100,000
Maximum period of sale to defer gain on sale of other property, days	180
Business Acquisition, Percentage of Voting Interests Acquired										48.20%
Real Estate Maximum Exposure to Loss								19,500,000
Minimum Percentage Of Taxable Income Distributed To Shareholders	90.00%
Unrecognized Tax Benefits	$ 0	$ 0
Number of Properties Exceeding Segment Reporting Threshold	0
Segment Reporting, Factors Used to Identify Entity's Reportable Segments	10% of our revenues or property operating income
Number of Segments	1