Acquired In-Place Leases (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 year	Dec. 31, 2010	Dec. 31, 2009
Above Market Leases [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Acquisition, Purchase Price Allocation, Amortizable Intangible Assets	$ 21,400,000	$ 20,600,000
Finite-Lived Intangible Assets, Accumulated Amortization	11,900,000	9,900,000
Amortization of Acquired Intangible Assets	2,400,000	2,000,000	2,500,000
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life	5.8
Amortization For Acquired In Place Leases [Abstract]
2012	1,841,000
2013	1,350,000
2014	1,277,000
2015	1,204,000
2016	922,000
Thereafter	2,977,000
Finite-Lived Intangible Assets, Future Amortization Expense	9,571,000
Below Market Leases [Member]
Acquired Finite-Lived Intangible Assets [Line Items]
Business Acquisition Purchase Price Allocation Amortizable Intangible Below Market Lease Liabilities	57,200,000	53,900,000
Acquired Below Market Lease Accumulated Amortization	26,300,000	23,500,000
Amortization Of Acquired Below Market Leases	3,800,000	3,600,000	4,200,000
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life	11.1
Amortization For Acquired In Place Leases [Abstract]
2012	3,535,000
2013	3,128,000
2014	2,551,000
2015	2,381,000
2016	2,129,000
Thereafter	17,271,000
Future Recognition of Deferred Revenue	$ 30,995,000