Summary of Significant Accounting Policies (Details 2) (USD $)	3 Months Ended		9 Months Ended
	Sep. 30, 2013	Sep. 30, 2012	Sep. 30, 2013	Sep. 30, 2012	Dec. 31, 2012
Tenant Accounts Receivable, net
Allowance for doubtful accounts	$ 4,000		$ 4,000		$ 0
Accrued rental revenue	8,500,000		8,500,000		6,400,000
Allowance on accrued rental revenue	0		0		0
Lease security deposits available in existing letters of credit	4,900,000		4,900,000		4,800,000
Lease security deposits available in cash	2,800,000		2,800,000		2,000,000
Deferred Costs
Amortization of deferred financing fees	300,000	300,000	900,000	900,000
Revenue Recognition
Estimated amount of real estate taxes, which are the responsibility of tenants	$ 2,400,000	$ 1,900,000	$ 7,000,000	$ 4,900,000