Investment in Unconsolidated Joint Ventures (Details) (USD $)	Sep. 30, 2014 sqft	Sep. 30, 2014 100 Park Avenue sqft		Sep. 30, 2014 717 Fifth Avenue sqft		Sep. 30, 2014 800 Third Avenue sqft		Sep. 30, 2014 1745 Broadway sqft		Sep. 30, 2014 1 and 2 Jericho Plaza sqft		Sep. 30, 2014 The Meadows sqft		Sep. 30, 2014 600 Lexington Avenue sqft		Sep. 30, 2014 11 West 34th Street sqft		Sep. 30, 2014 7 Renaissance sqft		Sep. 30, 2014 3 Columbus Circle sqft		Sep. 30, 2014 280 Park Avenue sqft		Sep. 30, 2014 1552-1560 Broadway sqft		Dec. 31, 2013 1552-1560 Broadway sqft	Sep. 30, 2014 724 Fifth Avenue sqft		Sep. 30, 2014 10 East 53rd Street sqft		Sep. 30, 2014 33 Beekman floor sqft		Sep. 30, 2014 521 Fifth Avenue sqft		Sep. 30, 2014 21 East 66th Street sqft		Sep. 30, 2014 21 East 66th Street Three retail units unit	Sep. 30, 2014 21 East 66th Street 2 residential units unit	Sep. 30, 2014 21 East 66th Street Four residential units unit	Sep. 30, 2014 315 West 36th Street sqft		Sep. 30, 2014 650 Fifth Avenue sqft		Oct. 31, 2014 650 Fifth Avenue Joint Venture Total floating rate Subsequent event	Sep. 30, 2014 121 Greene Street sqft
General information on each joint venture
Ownership Interest (as a percent)		49.90%		10.92%		42.95%		32.26%		20.26%		50.00%		55.00%		30.00%		50.00%		48.90%	[1]	50.00%		50.00%	[2]		50.00%		55.00%		45.90%	[3]	50.50%		32.28%	[4]	32.28%		16.14%	35.50%		50.00%	[5]		50.00%
Economic Interest (as a percent)		49.90%		10.92%		42.95%		32.26%		20.26%		50.00%		55.00%		30.00%		50.00%		48.90%	[1]	49.50%		50.00%	[2]		50.00%		55.00%		45.90%	[3]	50.50%		32.28%	[4]				35.50%		50.00%	[5]		50.00%
Area of property (sqft)	33,892,903	834,000		120,000		526,000		674,000		640,000		582,000		304,000		17,000		37,000		769,000	[1]	1,237,000		49,000	[2]	13,045	65,000		390,000		145,000	[3]	460,000		17,000	[4]				148,000		32,000	[5]		7,000
Acquisition Price		$ 95,800,000	[6]	$ 251,900,000	[6]	$ 285,000,000	[6]	$ 520,000,000	[6]	$ 210,000,000	[6]	$ 111,500,000	[6]	$ 193,000,000	[6]	$ 10,800,000	[6]	$ 4,000,000	[6]	$ 500,000,000	[1],[6]	$ 400,000,000	[6]	$ 136,550,000	[2],[6]		$ 223,000,000	[6]	$ 252,500,000	[6]	$ 31,000,000	[3],[6]	$ 315,000,000	[6]	$ 75,000,000	[4],[6]				$ 45,000,000	[6]	$ 0	[5],[6]		$ 28,200,000
Number of floors of student housing (floors)																															30
Number of units in property (units)																																					3	2	4
Face amount of loan																																												97,000,000
Initial funding on mortgage loan																																												$ 65,000,000

[1] As a result of the sale of a condominium interest in September 2012, Young & Rubicam, Inc., or Y&R, owns a portion of the property, generally floors three through eight referred to as Y&R units. Because the joint venture has an option to repurchase the Y&R units, the gain associated with this sale was deferred.

[2] The purchase price pertained only to the purchase of the 1552 Broadway interest which comprised 13,045 square feet. The joint venture also owns a long-term leasehold interest in the retail space and certain other spaces at 1560 Broadway, which is adjacent to 1552 Broadway.

[3] The joint venture owns a fee interest in the property and will develop an approximately 30 story building for student housing. Upon completion of the development, the joint venture will convey a long-term ground lease condominium interest in the building to Pace.

[4] We hold a 32.28% interest in three retail and two residential units at the property and a 16.14% interest in four residential units at the property.

[5] The joint venture owns a long-term leasehold interest in the retail space at 650 Fifth Avenue. In connection with the ground lease obligation, SLG provided a performance guaranty and Sutton executed a contribution agreement to reflect its pro rata obligation. In the event the property is converted into a condominium unit and the landlord elects the purchase option, the joint venture shall be obligated to acquire the unit at the then fair value. In October 2014, the joint venture closed on a $97.0 million floating rate leasehold mortgage with an initial funding of $65.0 million.

[6] Acquisition price represents the actual or implied gross purchase price for the joint venture.