Description of Business and Organization Description of Business and Organization Narrative (Details)	0 Months Ended	3 Months Ended
	Oct. 06, 2013 entity	Mar. 31, 2014 entity sqft
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property		8,400,000
OP units owned by the Company, percent		38.90%
Number of entities to be treated as taxable REIT subsidiary		2
Number of entities acquired	4	4
Office Building [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property		7,700,000
Number of properties		12
Office Building [Member] | Manhattan [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property		5,900,000
Number of properties		7
Office Building [Member] | Fairfield County, Connecticut and Westchester County, New York [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property		1,800,000
Number of properties		5
Development Parcel [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of properties		1
Retail Site [Member] | Manhattan and Westport, Connecticut [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property		204,175
Retail Site [Member] | Manhattan [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property		419,812
Number of properties		4
Retail Site [Member] | Westport, Connecticut [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Number of properties		2
Other Property [Member] | Stamford, Connecticut [Member]
Organization, Consolidation and Presentation of Financial Statements Disclosure [Line Items]
Area of real estate property		380,000