Investments in Unconsolidated Joint Ventures - Summary of Investments and Income from Investments In Unconsolidated Joint Ventures (Parenthetical) (Details) - USD ($) $ in Thousands		6 Months Ended	9 Months Ended
	May 05, 2017	Jun. 30, 2017	Sep. 30, 2017	Jun. 29, 2017	May 04, 2017
Schedule Of Equity Method Investments [Line Items]
Distributions of capital from unconsolidated joint ventures			$ 20,000
712 Fifth Avenue [Member]
Schedule Of Equity Method Investments [Line Items]
Basis of investment property				$ 4,928
Distributions of capital from unconsolidated joint ventures		$ 20,000
Property ownership, percentage		50.00%
RDF [Member] | 75 Howard [Member]
Schedule Of Equity Method Investments [Line Items]
Property ownership, percentage					100.00%
Ownership percentage in residential fund	7.40%		7.40%
Economic interest percentage	1.50%		1.50%