Significant Tenants (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended		9 Months Ended			1 Months Ended	9 Months Ended
	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014	Sep. 30, 2013	Sep. 30, 2014 Customer Concentration Risk [Member] Sales Revenue Services Net [Member] Minimum Threshold [Member]	Oct. 31, 2014 Bloomberg [Member] Subsequent Event [Member] 731 Lexington Avenue [Member] sqft	Sep. 30, 2014 Bloomberg [Member] Customer Concentration Risk [Member]	Sep. 30, 2013 Bloomberg [Member] Customer Concentration Risk [Member]	Sep. 30, 2014 Bloomberg [Member] Customer Concentration Risk [Member] Sales Revenue Services Net [Member]	Sep. 30, 2013 Bloomberg [Member] Customer Concentration Risk [Member] Sales Revenue Services Net [Member]
Real Estate Properties [Line Items]
Real estate revenue, net (in dollars)	$ 50,077	$ 49,886	$ 149,528	$ 145,963			$ 67,488	$ 65,938
Percentage Rent Contributed By Tenant, Minimum threshold					10.00%				45.00%	45.00%
Area of property (in square feet)						188,608
Lease renewal term						5 years