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Organization and Basis of Presentation - Additional Information (Details) - SL Green Operating Partnership	9 Months Ended
	Sep. 30, 2018	Dec. 31, 2017
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	100.00%
Noncontrolling interest in the operating partnership (as a percent)	5.10%	4.58%

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- Definition

The equity interest of noncontrolling shareholders, partners or other equity holders in consolidated entity.

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- Definition

The number of units or percentage investment held in the subsidiary by the limited liability company or limited partnership.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 946
-SubTopic 320
-Section S99
-Paragraph 9
-URI http://asc.fasb.org/extlink&oid=50485924&loc=d3e611443-123010

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