Property Acquisitions (Details) $ in Millions	Sep. 30, 2021 USD ($) ft²	Jun. 30, 2021 USD ($) ft²	Jan. 31, 2021 USD ($) ft²
Property Acquisitions
Area of Real Estate Property	28,035,572
885 Third Avenue
Property Acquisitions
Area of Real Estate Property			625,000
Gross Asset Valuation (in millions) | $			$ 387.9
461 Fifth Avenue
Property Acquisitions
Area of Real Estate Property		200,000
Gross Asset Valuation (in millions) | $		$ 28.0
1591-1597 Broadway (3)
Property Acquisitions
Area of Real Estate Property	7,684
Gross Asset Valuation (in millions) | $	$ 121.0
690 Madison Avenue
Property Acquisitions
Area of Real Estate Property	7,848
Gross Asset Valuation (in millions) | $	$ 72.2