Real Estate (Details Textual) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2012	Jun. 30, 2011	Jun. 30, 2012	Jun. 30, 2011
Real Estate (Textual) [Abstract]
Total revenue of specific real estate properties	$ 2,845,000	$ 2,484,000	$ 5,563,000	$ 4,401,000
Operating expenses of specific real estate properties	40,559,000	37,574,000	80,264,000	69,084,000
Operating income(loss) of specific real estate properties	17,250,000	13,526,000	34,583,000	28,899,000
Net income	2,624,000	455,000	5,495,000	14,051,000
Beach Street [Member]
Real Estate (Textual) [Abstract]
Date of Acquisition			Jan. 24, 2012
Weighted average life			7 years 0 months 0 days
Total revenue of specific real estate properties			1,900,000
Operating expenses of specific real estate properties			1,200,000
Operating income(loss) of specific real estate properties			700,000
Net income			400,000
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