Acquisitions (Details Textuals) (USD $) In Thousands, unless otherwise specified	3 Months Ended
	Mar. 31, 2012 Years
Aquisitions (Textuals) [Abstract]
Number of Buildings	7
In-Place Leases [Member]
Aquisitions (Textuals) [Abstract]
Deferred leasing costs and acquisition-related intangible assets	$ 5,800
Weighted average amortization period in years	5.8
Above-Market Leases [Member]
Aquisitions (Textuals) [Abstract]
Deferred leasing costs and acquisition-related intangible assets	100
Weighted average amortization period in years	2.6
Deferred Leasing Costs [Member]
Aquisitions (Textuals) [Abstract]
Deferred leasing costs and acquisition-related intangible assets	3,500
Weighted average amortization period in years	4.3
Below-Market Leases [Member]
Aquisitions (Textuals) [Abstract]
Deferred revenue and acquisition-related intangible liabilities	$ 10,400
Weighted average amortization period in years	8.2