Investments in Unconsolidated Joint Ventures - Summary of Investments and Income from Investments In Unconsolidated Joint Ventures (Parenthetical) (Details) - USD ($)		12 Months Ended
	Jan. 01, 2018	Dec. 31, 2019	Dec. 31, 2018
Schedule Of Equity Method Investments [Line Items]
Adjustment to investments in unconsolidated joint ventures			$ 7,086,000
712 Fifth Avenue [Member]
Schedule Of Equity Method Investments [Line Items]
Distributions made in excess of share of earnings recognized negative basis		$ 19,648
55 Second Street [Member]
Schedule Of Equity Method Investments [Line Items]
Difference between carrying amount of investment and equity		583,000
60 Wall Street [Member]
Schedule Of Equity Method Investments [Line Items]
Difference between carrying amount of investment and equity		2,716,000
One Steuart Lane [Member]
Schedule Of Equity Method Investments [Line Items]
Difference between carrying amount of investment and equity		974,000
One Steuart Lane [Member] | ASU 2017-05 [Member] | RDF [Member]
Schedule Of Equity Method Investments [Line Items]
Adjustment to investments in unconsolidated joint ventures	$ 7,086,000
Oder-Center, Germany [Member]
Schedule Of Equity Method Investments [Line Items]
Difference between carrying amount of investment and equity		$ 4,576,000