Disposal Group Including Discontinued Operation, Ownership Percentage In Disposed Investment

No definition available.

Name:	slg_DisposalGroupIncludingDiscontinuedOperationOwnershipPercentageInDisposedInvestment
Namespace Prefix:	slg_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Extinguishment Of Secured Debt, Bearing Fixed Interest, Amount

+ References

No definition available.

+ Details

Name:	slg_ExtinguishmentOfSecuredDebtBearingFixedInterestAmount
Namespace Prefix:	slg_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

Represents the number of shares of the common stock of the entity, which the limited partner of the operating partnership is entitled to receive on redemption of one unit of interest in the partnership.

+ References

No definition available.

+ Details

Name:	slg_NumberOfSharesOnRedemptionOfOneUnitOfPartnershipInterest
Namespace Prefix:	slg_
Data Type:	xbrli:sharesItemType
Balance Type:	na
Period Type:	duration

- Definition

Number of Real Estate Buildings

+ References

No definition available.

+ Details

Name:	slg_NumberofRealEstateBuildings
Namespace Prefix:	slg_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

-- None. No documentation exists for this element. --

+ References

No definition available.

+ Details

Name:	slg_OwnershipInterestsLineItems
Namespace Prefix:	slg_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The portion of the carrying amount of long-term secured loans outstanding as of the balance sheet date, including current maturities, which accrues interest at a set, unchanging rate.

+ References

No definition available.

+ Details

Name:	slg_SecuredDebtBearingFixedInterestAmount
Namespace Prefix:	slg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Secured Debt, Bearing Fixed Interest, Mezzanine Loan Amount

+ References

No definition available.

+ Details

Name:	slg_SecuredDebtBearingFixedInterestMezzanineLoanAmount
Namespace Prefix:	slg_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Secured Debt, Bearing Fixed Interest, Term

+ References

No definition available.

+ Details

Name:	slg_SecuredDebtBearingFixedInterestTerm
Namespace Prefix:	slg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	instant

- Definition

Area of a real estate property.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 275
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482861/275-10-50-2

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.12-28(Column A)(Footnote 2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478979/970-360-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 970
-SubTopic 360
-Name Accounting Standards Codification
-Section 30
-Paragraph 2
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478150/970-360-30-2

+ Details

Name:	us-gaap_AreaOfRealEstateProperty
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:areaItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of consideration received or receivable for the disposal of assets and liabilities, including discontinued operation.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 360
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 3
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482099/360-10-50-3

+ Details

Name:	us-gaap_DisposalGroupIncludingDiscontinuedOperationConsideration
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant

- Definition

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

+ References

No definition available.

+ Details

Name:	us-gaap_MinorityInterestOwnershipPercentageByNoncontrollingOwners
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Details

Name:	us-gaap_RelatedPartyTransactionsByRelatedPartyAxis=us-gaap_CorporateJointVentureMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=slg_A245ParkAvenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_AllianzRealEstateOfAmericaMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_RealEstateAndAccumulatedDepreciationDescriptionOfPropertyAxis=slg_A650FifthAvenueMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ScheduleOfEquityMethodInvestmentEquityMethodInvesteeNameAxis=slg_WhartonPropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=slg_FoodAndBeverageHospitalityCompanyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=slg_A185BroadwayMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_IncomeStatementBalanceSheetAndAdditionalDisclosuresByDisposalGroupsIncludingDiscontinuedOperationsAxis=slg_A110GreeneStreetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=srt_OfficeBuildingMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_MortgageLoansOnRealEstateDescriptionTypeOfPropertyAxis=slg_ManagedOfficePropertiesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_OwnershipAxis=slg_OperatingPartnershipMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ConsolidatedEntitiesAxis=srt_SubsidiariesMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Organization and Basis of Presentation - Additional Information (Details) $ in Thousands, ft² in Millions	9 Months Ended
	Sep. 30, 2026 USD ($) ft² building shares	Nov. 04, 2026 USD ($)	Oct. 31, 2026 USD ($)	Dec. 31, 2025 USD ($)
Organization
Number of shares to be received on redemption of one unit of limited partnership interests (shares) \| shares	1
Total fixed rate debt	$ 2,159,386			$ 2,075,222
Due from joint ventures
Organization
Total fixed rate debt	12,387,080			10,791,783
245 Park Avenue \| Allianz Real Estate of America \| Due from joint ventures
Organization
Total fixed rate debt	1,768,000			1,768,000
650 Fifth Avenue \| Wharton Properties \| Due from joint ventures
Organization
Total fixed rate debt	$ 65,000			$ 65,000
Subsequent Event \| 245 Park Avenue \| Allianz Real Estate of America \| Due from joint ventures
Organization
Total fixed rate debt			$ 2,000,000
Fixed interest term			5 years
Subsequent Event \| 650 Fifth Avenue \| Wharton Properties \| Due from joint ventures
Organization
Extinguishment of secured debt, bearing fixed interest, amount			$ 65,000
Secured debt, bearing fixed interest, mezzanine loan amount			$ 2,000
Subsequent Event \| Food And Beverage Hospitality Company
Organization
Disposal group, including discontinued operation, ownership percentage in disposed investment			20.00%
Sales price			$ 200,000
Subsequent Event \| 185 Broadway
Organization
Sales price			$ 9,000
Subsequent Event \| 110 Greene Street
Organization
Sales price		$ 226,000
Office Building
Organization
Number of buildings \| building	5
Managed Office Properties
Organization
Unaudited Approximate Square Feet \| ft²	1.3
Operating Partnership \| SL Green Operating Partnership
Organization
Noncontrolling interest in the operating partnership (as a percent)	6.95%			6.42%