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Properties Held for Sale and Property Dispositions (Details) $ in Millions | 1 Months Ended | 9 Months Ended
--- | --- | ---
Jul. 31, 2021 USD ($) ft² | Jun. 30, 2021 USD ($) ft² | Mar. 31, 2021 USD ($) ft² | Feb. 28, 2021 USD ($) ft² | Jan. 31, 2021 USD ($) ft² | Sep. 30, 2021 USD ($) ft²
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |
Area of Real Estate Property | ft² |  |  |  |  |  | 28,035,572
220 East 42nd Street | 220 East 42nd Street |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |
Ownership percentage deconsolidated | 51.00% |  |  |  |  |
Investment fair value adjustment |  |  |  |  |  | $ 206.8
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 |  |  |  |  |  |
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) |  |  |
635-641 Sixth Avenue |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |
Area of Real Estate Property | ft² |  | 267,000 |  |  |  |
Sales Price |  | $ 325.0 |  |  |  |
Gain (loss) |  | $ 99.4 |  |  |  |
220 East 42nd Street |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |
Area of Real Estate Property | ft² | 1,135,000 |  |  |  |  |
Sales Price | $ 783.5 |  |  |  |  |
Gain (loss) | $ 175.1 |  |  |  |  |
Ownership interest disposed | 49.00% |  |  |  |  |
Properties Sold In 2021 |  |  |  |  |  |
Income Statement, Balance Sheet and Additional Disclosures by Disposal Groups, Including Discontinued Operations [Line Items] |  |  |  |  |  |
Employee-related liabilities |  |  |  |  |  | $ 11.7

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