Properties Held for Sale and Property Dispositions (Details) $ in Millions	1 Months Ended
	Mar. 31, 2021 USD ($) ft²	Feb. 28, 2021 USD ($) ft²	Jan. 31, 2021 USD ($) ft²
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of Real Estate Property | ft²	29,134,784
712 Madison Avenue
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of Real Estate Property | ft²			6,600
Sales Price			$ 43.0
Gain (loss)			$ (1.4)
133 Greene Street
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of Real Estate Property | ft²		6,425
Sales Price		$ 15.8
Gain (loss)		$ 0.2
106 Spring Street (2)
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items]
Area of Real Estate Property | ft²	5,928
Sales Price	$ 35.0
Gain (loss)	$ (2.8)