Other Assets (Details Textual) (USD $) In Thousands, unless otherwise specified	9 Months Ended
	Sep. 30, 2012	Dec. 31, 2011
Other Assets (Textual) [Abstract]
Net of accumulated amortization of leasing commissions	$ 17,107	$ 14,722
Net of accumulated amortization of lease incentives	2,128	1,850
Net of accumulated amortization of other intangible assets	4,208	3,885
Net of accumulated amortization of debt issuance costs	$ 2,476	$ 2,509
Acquisition completion date	Jan. 24, 2012
One Beach Street [Member]
Other Assets (Textual) [Abstract]
Acquisition completion date	Jan. 24, 2012