Real Estate (Details Textual) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2012	Sep. 30, 2011	Sep. 30, 2012	Sep. 30, 2011
Real Estate (Textual) [Abstract]
Date of acquisition			Jan. 24, 2012
Weighted average life			5 years 9 months 18 days
Total revenue of specific real estate properties	$ 2,921,000	$ 3,015,000	$ 8,484,000	$ 7,416,000
Operating expenses of specific real estate properties	43,716,000	41,137,000	123,980,000	110,222,000
Operating income(loss) of specific real estate properties	19,120,000	15,156,000	53,703,000	44,054,000
Net income	4,285,000	4,618,000	9,780,000	18,669,000
Purchase price of a specific real estate property			228,800,000
Closing costs for a specific real estate property			100,000
Approximate additional credits received to purchase price			6,900,000
Beach Street [Member]
Real Estate (Textual) [Abstract]
Weighted average life			7 years 0 months 0 days
Total revenue of specific real estate properties			2,900,000
Operating expenses of specific real estate properties			700,000
Operating income(loss) of specific real estate properties			2,200,000
Net income			600,000
Number of stories in a real estate property	3		3
Purchase price of a specific real estate property			36,500,000
Closing costs for a specific real estate property			20,000
Rentable square feet of a specific real estate property	97,000		97,000
City Center [Member]
Real Estate (Textual) [Abstract]
Date of acquisition			Aug. 21, 2012
Weighted average life			5 years 9 months 18 days
Total revenue of specific real estate properties			2,200,000
Operating expenses of specific real estate properties			400,000
Operating income(loss) of specific real estate properties			1,800,000
Net income			100,000
Number of stories in a real estate property	27		27
Rentable square feet of a specific real estate property	497,000		497,000
Geary Marketplace [Member]
Real Estate (Textual) [Abstract]
Date of acquisition			Aug. 30, 2012
Purchase price of a specific real estate property			21,000,000
Rentable square feet of a specific real estate property	35,000		35,000
Lease percentage of property			100.00%
Valencia Corporate Center [Member]
Real Estate (Textual) [Abstract]
Tax related reserves	300,000
Tax related to discontinued operations	$ 200,000