Acquired Lease Intangibles (Details) (USD $)	12 Months Ended
	Dec. 31, 2011 years	Dec. 31, 2010	Dec. 31, 2009
Finite-Lived Intangible Assets [Line Items]
Off-market Lease, Unfavorable	$ 12,700,000	$ 6,700,000
Weighted Average Accretion Period of Intangible Liabilities (in years)	11.9
Accretion Expense	1,400,000	1,300,000	1,900,000
Leases, Acquired-in-Place [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired lease intangible assets, net of amortization	27,100,000	21,900,000
Accumulated amortization	18,200,000	15,700,000
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life (in years)	13.0
Finite-Lived Intangible Assets, Amortization Expense	3,400,000	2,300,000	2,700,000
Above Market Lease [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired lease intangible assets, net of amortization	3,400,000	1,000,000
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life (in years)	6.8
Finite-Lived Intangible Assets, Amortization Expense	319,000	108,000	102,000
Above Market Ground Rent Lease [Member]
Finite-Lived Intangible Assets [Line Items]
Acquired lease intangible assets, net of amortization	$ 1,700,000	$ 1,600,000
Acquired Finite-lived Intangible Asset, Weighted Average Useful Life (in years)	85.5