Debt Instrument, Face Amount, Higher Borrowing Capacity Option

No definition available.

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

- Definition

Debt Instrument, Face Amount, Limit Increase

+ References

No definition available.

+ Details

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

- Definition

Debt Instrument, Number of Extension Options

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument, Period of Extension Option

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Line Of Credit Facility, Number Of Extensions

+ References

No definition available.

+ Details

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

- Definition

The expanded maximum borrowing capacity available, which is subject to agreement with the entity.

+ References

No definition available.

+ Details

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

- Definition

Line Of Credit Facility, Term Of Extension

+ References

No definition available.

+ Details

Name:	slg_LineOfCreditFacilityTermOfExtension
Namespace Prefix:	slg_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Percentage points added to the reference rate to compute the variable rate on the debt instrument.

+ References

No definition available.

+ Details

Name:	us-gaap_DebtInstrumentBasisSpreadOnVariableRate1
Namespace Prefix:	us-gaap_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Face (par) amount of debt instrument at time of issuance.

+ References

+ Details

Name:	us-gaap_DebtInstrumentFaceAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Effective interest rate for the funds borrowed under the debt agreement considering interest compounding and original issue discount or premium.

+ References

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line items represent financial concepts included in a table. These concepts are used to disclose reportable information associated with domain members defined in one or many axes to the table.

+ References

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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

Name:	us-gaap_LettersOfCreditOutstandingAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The carrying value as of the balance sheet date of the current and noncurrent portions of long-term obligations drawn from a line of credit, which is a bank's commitment to make loans up to a specific amount. Examples of items that might be included in the application of this element may consist of letters of credit, standby letters of credit, and revolving credit arrangements, under which borrowings can be made up to a maximum amount as of any point in time conditional on satisfaction of specified terms before, as of and after the date of drawdowns on the line. Includes short-term obligations that would normally be classified as current liabilities but for which (a) postbalance sheet date issuance of a long term obligation to refinance the short term obligation on a long term basis, or (b) the enterprise has entered into a financing agreement that clearly permits the enterprise to refinance the short-term obligation on a long term basis and the following conditions are met (1) the agreement does not expire within 1 year and is not cancelable by the lender except for violation of an objectively determinable provision, (2) no violation exists at the BS date, and (3) the lender has entered into the financing agreement is expected to be financially capable of honoring the agreement.

+ References

+ Details

Name:	us-gaap_LineOfCredit
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The fee, expressed as a percentage of the line of credit facility, for the line of credit facility regardless of whether the facility has been used.

+ References

No definition available.

+ Details

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Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Maximum borrowing capacity under the credit facility without consideration of any current restrictions on the amount that could be borrowed or the amounts currently outstanding under the facility.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
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+ Details

Name:	us-gaap_LineOfCreditFacilityMaximumBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount of borrowing capacity currently available under the credit facility (current borrowing capacity less the amount of borrowings outstanding).

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityRemainingBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Amount, after deduction of unamortized premium (discount) and debt issuance cost, of long-term debt. Excludes lease obligation.

+ References

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+ Details

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Balance Type:	credit
Period Type:	instant

- Details

Name:	us-gaap_DebtInstrumentAxis=slg_TermLoanAMaturityMay2026Member
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Name:	us-gaap_DebtInstrumentAxis=slg_TermLoanBMaturityNovember2024Member
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- Details

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Corporate Indebtedness - Additional Information (Details)	1 Months Ended	6 Months Ended
	Oct. 31, 2022 USD ($) extensionOption	Jun. 30, 2023 USD ($) extension	Jan. 31, 2023 USD ($)	Dec. 31, 2022 USD ($)
Corporate Indebtedness
Revolving credit facility, net		$ 423,985,000		$ 443,217,000
Term Loan A, Maturity May 2026 \| Term Loan
Corporate Indebtedness
Maximum facility capacity		$ 1,050,000,000.00
Term Loan A, Maturity May 2026 \| SOFR \| Term Loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)		1.20%
Term Loan A, Maturity May 2026 \| SOFR \| Minimum \| Term Loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)		0.80%
Term Loan A, Maturity May 2026 \| SOFR \| Maximum \| Term Loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)		1.60%
Term Loan B, Maturity November 2024 \| Term Loan
Corporate Indebtedness
Maximum facility capacity		$ 200,000,000
Term Loan B, Maturity November 2024 \| SOFR \| Term Loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)		1.25%
Term Loan B, Maturity November 2024 \| SOFR \| Minimum \| Term Loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)		0.85%
Term Loan B, Maturity November 2024 \| SOFR \| Maximum \| Term Loan
Corporate Indebtedness
Interest rate added to base rate (as a percent)		1.65%
Revolving Credit Facility
Corporate Indebtedness
Facility fee (as a percent)		0.25%
Revolving credit facility, net		$ 430,000,000
Revolving Credit Facility \| Minimum
Corporate Indebtedness
Facility fee (as a percent)		0.125%
Revolving Credit Facility \| Maximum
Corporate Indebtedness
Facility fee (as a percent)		0.30%
Term Loan
Corporate Indebtedness
Long-term debt, carrying value		$ 1,250,000,000
Term Loan \| Line of Credit
Corporate Indebtedness
Long-term debt, carrying value		1,200,000,000		1,200,000,000
2012 Credit Facility
Corporate Indebtedness
Letters of credit		2,000,000
Ability to borrow under line of credit facility		820,000,000
2012 Credit Facility \| Line of Credit
Corporate Indebtedness
Long-term debt, carrying value		$ 424,000,000		443,200,000
Revolving Credit Facility \| SOFR \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)		0.10%
Revolving Credit Facility \| Revolving Credit Facility, Maturity May 2026 \| Line of Credit
Corporate Indebtedness
Maximum facility capacity		$ 1,250,000,000
Number of extensions \| extension		2
Term of extension		6 months
Maximum borrowing capacity, optional expansion		$ 4,500,000,000
Revolving Credit Facility \| Revolving Credit Facility, Maturity May 2026 \| SOFR \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)		1.05%
Revolving Credit Facility \| Revolving Credit Facility, Maturity May 2026 \| SOFR \| Minimum \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)		0.725%
Revolving Credit Facility \| Revolving Credit Facility, Maturity May 2026 \| SOFR \| Maximum \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)		1.40%
Line of Credit \| Term Loan 2022 \| Line of Credit
Corporate Indebtedness
Long-term debt, carrying value		$ 423,700,000		$ 398,200,000
Debt instrument face amount		$ 425,000,000	$ 425,000,000
Number of extension options \| extensionOption	1
Period of extension options	6 months
Debt instrument, face amount, higher borrowing capacity option	$ 500,000,000
Debt instrument, face amount, increase limit			$ 25,000,000
Line of Credit \| Term Loan 2022 \| SOFR \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)		0.10%
Debt instrument, interest rate, effective percentage				1.40%
Line of Credit \| Term Loan 2022 \| SOFR \| Minimum \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)		1.00%
Line of Credit \| Term Loan 2022 \| SOFR \| Maximum \| Line of Credit
Corporate Indebtedness
Interest rate added to base rate (as a percent)		1.80%