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Partners' Capital of the Operating Partnership - Additional Information (Details) | 12 Months Ended |  |  |
--- | --- | --- | --- | ---
Dec. 31, 2019 shares | Dec. 31, 2018 unit shares | Dec. 31, 2017 shares | Dec. 31, 2016 shares
Common Stock |  |  |  |
Stockholders' Equity |  |  |  |
Units, outstanding | 79,202,000 | 83,684,000 | 92,803,000 | 100,562,000
SL Green Operating Partnership |  |  |  |
Stockholders' Equity |  |  |  |
Noncontrolling interest in the operating partnership (as a percent) | 5.03% | 4.70% |  |
Number of units of operating partnership owned by the noncontrolling interest unit holders (units) | 4,195,875 | 4,130,579 |  |
SL Green Operating Partnership | Series I Preferred Units |  |  |  |
Stockholders' Equity |  |  |  |
Units, outstanding | 9,200,000 |  |  |
Common units redemption, period of restriction | 1 year |  |  |
Conversion of stock, shares issued (in shares) | 1 |  |  |
SL Green Operating Partnership | Common Stock |  |  |  |
Stockholders' Equity |  |  |  |
Units, outstanding | 79,202,322 |  |  |

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