XML 111 R88.htm IDEA: XBRL DOCUMENT
v3.25.0.1

Debt and Preferred Equity Investments - Schedule of Activity in Debt and Preferred Equity Investments (Details) $ in Thousands | 12 Months Ended
--- | ---
Dec. 31, 2024 USD ($) investment | Dec. 31, 2023 USD ($) investment
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward] |  |
Balance at beginning of year | $ 346,745 | $ 623,280
Redemptions/sales/syndications/equity ownership/amortization | (64,629) | (349,947)
Net change in loan loss reserves | 0 | (6,890)
Balance at end of period | 303,726 | 346,745
Carrying Value | $ 303,726 | $ 346,745
Number of investments, nonperforming | investment | 2 | 2
Total floating rate |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward] |  |
Carrying Value | $ 117,160 | $ 168,899
Total floating rate | Alternative strategy portfolio |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward] |  |
Carrying Value | 53,500 |
Debt Investment |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward] |  |
Originations/fundings/accretion | 12,890 | 72,160
Preferred Equity Investments |  |
SEC Schedule, 12-29, Real Estate Companies, Investment in Movement in Mortgage Loans on Real Estate [Roll Forward] |  |
Originations/fundings/accretion | $ 8,720 | $ 8,142

X
- Definition Number Of Investments, Nonperforming + References No definition available. + Details
Name: | slg_NumberOfInvestmentsNonperforming
Namespace Prefix: | slg_
Data Type: | xbrli:integerItemType
Balance Type: | na
Period Type: | instant

X
- Definition SEC Schedule, 12-29, Real Estate Companies, Investment In Mortgage Loans On Real Estate, Loan Loss Reserve Period Increase (Decrease) + References No definition available. + Details
Name: | slg_SECSchedule1229RealEstateCompaniesInvestmentInMortgageLoansOnRealEstateLoanLossReservePeriodIncreaseDecrease
Namespace Prefix: | slg_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition Amount of investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 948 -SubTopic 310 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-29(Column G)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1 + Details
Name: | us-gaap_MortgageLoansOnRealEstate
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of decrease in investment in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, from amortization of premium. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 948 -SubTopic 310 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-29(Column G)(Footnote 6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1 + Details
Name: | us-gaap_MortgageLoansOnRealEstateAmortizationOfPremium
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | credit
Period Type: | duration

X
- Definition The balance represents the amount of loans that are secured by real estate mortgages, offset by the reserve to cover probable credit losses on the loan portfolio. + References Reference 1: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 14 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480078/944-80-55-14 Reference 2: http://www.xbrl.org/2003/role/exampleRef -Topic 944 -SubTopic 80 -Name Accounting Standards Codification -Section 55 -Paragraph 9 -Publisher FASB -URI https://asc.fasb.org/1943274/2147480078/944-80-55-9 Reference 3: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(1)(c)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 Reference 4: http://www.xbrl.org/2003/role/disclosureRef -Topic 944 -SubTopic 210 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.7-03(a)(1)(6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1 + Details
Name: | us-gaap_MortgageLoansOnRealEstateCommercialAndConsumerNet
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | instant

X
- Definition Amount of increase in mortgage loan on real estate by entity with substantial portion of business acquiring and holding investment real estate or interest in real estate, from new investment. + References Reference 1: http://www.xbrl.org/2003/role/disclosureRef -Topic 948 -SubTopic 310 -Name Accounting Standards Codification -Section S99 -Paragraph 1 -Subparagraph (SX 210.12-29(Column G)(Footnote 6)) -Publisher FASB -URI https://asc.fasb.org/1943274/2147479628/948-310-S99-1 + Details
Name: | us-gaap_MortgageLoansOnRealEstateNewMortgageLoans
Namespace Prefix: | us-gaap_
Data Type: | xbrli:monetaryItemType
Balance Type: | debit
Period Type: | duration

X
- Definition A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period. + References No definition available. + Details
Name: | us-gaap_MovementInMortgageLoansOnRealEstateRollForward
Namespace Prefix: | us-gaap_
Data Type: | xbrli:stringItemType
Balance Type: | na
Period Type: | duration

X
- Details
Name: | us-gaap_LongtermDebtTypeAxis=slg_DebtInvestmentWithFloatingInterestRateMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | slg_PortfolioAxis=slg_AlternativeStrategyPortfolioMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=slg_DebtInvestmentsInMortgageLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |

X
- Details
Name: | us-gaap_InvestmentTypeAxis=slg_PreferredEquityInvestmentsInMortgageLoansMember
Namespace Prefix: |
Data Type: | na
Balance Type: |
Period Type: |