Organization and Basis of Presentation - Additional Information (Details)	12 Months Ended
Dec. 31, 2020
SLG Management LLC \| SL Green Management
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	100.00%
Service Corporation
Organization
Percentage of ownership in SL Green Management LLC owned by operating partnership (percent)	95.00%

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

No definition available.

Name:	us-gaap_SubsidiaryOfLimitedLiabilityCompanyOrLimitedPartnershipOwnershipInterest
Namespace Prefix:	us-gaap_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration