Significant Tenants (Details) (USD $)	3 Months Ended		6 Months Ended
	Jun. 30, 2014	Jun. 30, 2013	Jun. 30, 2014	Jun. 30, 2013
Real Estate Properties [Line Items]
Real estate revenue, net (in dollars)	$ 49,983,000	$ 47,302,000	$ 99,451,000	$ 96,077,000
Sales Revenue Services Net [Member] | Minimum Threshold [Member]
Real Estate Properties [Line Items]
Percentage Rent Contributed By Tenant			10.00%
Bloomberg [Member] | Customer Concentration Risk [Member]
Real Estate Properties [Line Items]
Real estate revenue, net (in dollars)			$ 44,483,000	$ 43,322,000
Bloomberg [Member] | Customer Concentration Risk [Member] | Sales Revenue Services Net [Member]
Real Estate Properties [Line Items]
Percentage Rent Contributed By Tenant			45.00%	45.00%