Mortgages Payable (Details) (USD $)	6 Months Ended	12 Months Ended
	Jun. 30, 2012 item	Dec. 31, 2011
Mortgages Payable
Assumed mortgages payable		$ 67,400,000
Debt instrument
Remaining Principal Balance	56,198,000	67,150,000
Amortized Premium (Discount) Balance	463,000	631,000
Mortgage Payable Balance	56,661,000	67,781,000
Mortgages Payable
Debt instrument
Number of mortgages repaid	1
Amount repaid	10,700,000
Net premiums recorded upon assumption of mortgages		820,000
Deferred financing costs incurred		917,000
Remaining balance of deferred financing costs at period end	593,000	751,000
Mortgages maturing 5/6/12
Debt instrument
Stated Interest Rate (as a percent)		5.89%
Effective Interest Rate (as a percent)		5.19%
Remaining Principal Balance		10,664,000
Amortized Premium (Discount) Balance		26,000
Mortgage Payable Balance		10,690,000
Mortgages maturing 12/1/13
Debt instrument
Stated Interest Rate (as a percent)	6.25%	6.25%
Effective Interest Rate (as a percent)	4.62%	4.63%
Remaining Principal Balance	12,202,000	12,410,000
Amortized Premium (Discount) Balance	266,000	314,000
Mortgage Payable Balance	12,468,000	12,724,000
Number of properties occupied by applicable tenant	1	1
Mortgages maturing 9/1/14
Debt instrument
Stated Interest Rate (as a percent)	6.25%	6.25%
Effective Interest Rate (as a percent)	5.12%	5.09%
Remaining Principal Balance	11,591,000	11,671,000
Amortized Premium (Discount) Balance	255,000	359,000
Mortgage Payable Balance	11,846,000	12,030,000
Number of properties occupied by applicable tenant	1	1
Mortgages maturing 6/10/15
Debt instrument
Stated Interest Rate (as a percent)	4.74%	4.73%
Effective Interest Rate (as a percent)	4.84%	4.84%
Remaining Principal Balance	23,625,000	23,625,000
Amortized Premium (Discount) Balance	(58,000)	(68,000)
Mortgage Payable Balance	23,567,000	23,557,000
Floating variable interest rate, variable rate basis	1 month LIBOR	1 month LIBOR
Floating variable interest rate, basis spread on variable rate (as a percent)	4.50%	4.50%
Maximum interest rate (as a percent)	5.50%	5.50%
Mortgages one maturing 12/28/13
Debt instrument
Stated Interest Rate (as a percent)	8.26%	8.26%
Effective Interest Rate (as a percent)	8.26%	8.26%
Remaining Principal Balance	4,510,000	4,510,000
Mortgage Payable Balance	4,510,000	4,510,000
Number of properties occupied by applicable tenant	1	1
Mortgages two maturing 12/28/13
Debt instrument
Stated Interest Rate (as a percent)	8.26%	8.26%
Effective Interest Rate (as a percent)	8.26%	8.26%
Remaining Principal Balance	4,270,000	4,270,000
Mortgage Payable Balance	4,270,000	4,270,000
Number of properties occupied by applicable tenant	1	1
Mortgages maturing 12/28/13
Debt instrument
Note receivable acquired in connection with 2011 acquisition	$ 8,800,000	$ 8,800,000
Assumed note receivable stated interest rate (as a percent)	8.14%	8.14%