Property Acquisitions (Details) (USD $)	3 Months Ended		6 Months Ended		0 Months Ended
	Jun. 30, 2014 sqft	Jun. 30, 2013	Jun. 30, 2014 sqft	Jun. 30, 2013	May 31, 2014 Greenwich Street 388-390	May 31, 2014 Greenwich Street 388-390 sqft	Mar. 31, 2014 Mixed-Use Residential and Commercial Property 315 West 33rd Street	Nov. 30, 2013 Mixed-Use Residential and Commercial Property 315 West 33rd Street sqft
Business Acquisition [Line Items]
Economic interest						49.65%
Area of property (sqft)	33,867,788		33,867,788			2,400,000		492,987
Notional Value						$ 504,000,000
Real Estate fair value						1,585,000,000
Payment for property								386,800,000
Term					4 years
Face amount of loan						1,500,000,000
Debt refinanced					1,100,000,000
Interest rate added to base rate (as a percent)					1.75%
Purchase price fair value adjustment	71,446,000	(2,305,000)	71,446,000	(2,305,000)	71,400,000
Land								116,000,000
Building								270,800,000
Above-market and in-place leases							33,200,000
Below market leases							$ 7,800,000