Investments in Unconsolidated Joint Ventures - Additional Information (Details)			12 Months Ended
	May 05, 2017 USD ($)	Jan. 24, 2017 USD ($) ft²	Dec. 31, 2017 ft²	May 04, 2017
Schedule Of Equity Method Investments [Line Items]
Area of office and retail properties | ft²			12,500,000
RDF [Member]
Schedule Of Equity Method Investments [Line Items]
Ownership percentage in residential fund	7.40%		7.40%
75 Howard [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method ownership percentage			20.00%
75 Howard [Member] | RDF [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method ownership percentage	20.00%
Property ownership, percentage				100.00%
Percentage of equity interest sold by development fund	80.00%
Proceeds from sale of equity interest, by development fund	$ 88,000,000
Gain from sale of equity interest, by development fund	23,406,000
Entity's portion of gain from sale of equity interest, net of tax	$ 1,661,000
Property funds, ownership percentage	1.50%		1.50%
60 Wall Street [Member]
Schedule Of Equity Method Investments [Line Items]
Equity method ownership percentage		5.00%
Area of office and retail properties | ft²		1,600,000
Acquisition amount		$ 1,040,000,000
Mortgage financing amount		$ 575,000,000