Capitalization rate leverage ratio.

No definition available.

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Balance Type:	na
Period Type:	duration

- Definition

Credit facility cross default provision amount.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Credit Facility increase commitments.

+ References

No definition available.

+ Details

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Balance Type:	credit
Period Type:	instant

- Definition

Credit facility non-recourse debt.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Definition

Debt instrument origination fee amount.

+ References

No definition available.

+ Details

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Balance Type:	debit
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- Definition

Debt instrument percentage of origination fee.

+ References

No definition available.

+ Details

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- Definition

Fixed charge coverage ratio.

+ References

No definition available.

+ Details

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Balance Type:	na
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- Definition

Line of credit facility additional borrowing capacity.

+ References

No definition available.

+ Details

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Namespace Prefix:	stsff_
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Balance Type:	credit
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- Definition

Line of credit facility extension period.

+ References

No definition available.

+ Details

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- Definition

Line of credit facility sublimits.

+ References

No definition available.

+ Details

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Balance Type:	credit
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- Definition

Number of operating properties.

+ References

No definition available.

+ Details

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Period Type:	duration

- Definition

Number of self storage real estate joint ventures.

+ References

No definition available.

+ Details

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- Definition

Secured debt ratio.

+ References

No definition available.

+ Details

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- Definition

Unsecured interest coverage ratio.

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No definition available.

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- Definition

Amount of direct costs of the business combination including legal, accounting, and other costs incurred to consummate the business acquisition.

+ References

No definition available.

+ Details

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- Definition

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

+ References

No definition available.

+ Details

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- Definition

Amount, before unamortized (discount) premium and debt issuance costs, of long-term debt. Includes, but is not limited to, notes payable, bonds payable, commercial loans, mortgage loans, convertible debt, subordinated debt and other types of debt.

+ References

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- Definition

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

+ References

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Period Type:	instant

- Definition

Contractual interest rate for funds borrowed, under the debt agreement.

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- 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.

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+ Details

Name:	us-gaap_DebtInstrumentLineItems
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Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Period of time between issuance and maturity of debt instrument, in PnYnMnDTnHnMnS' format, for example, 'P1Y5M13D' represents the reported fact of one year, five months, and thirteen days.

+ References

No definition available.

+ Details

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Balance Type:	na
Period Type:	duration

- Definition

Weighted average interest rate of debt outstanding.

+ References

No definition available.

+ Details

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Namespace Prefix:	us-gaap_
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Balance Type:	na
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.

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

- Definition

Amount of current borrowing capacity under the credit facility considering any current restrictions on the amount that could be borrowed (for example, borrowings may be limited by the amount of current assets), but without considering any amounts currently outstanding under the facility.

+ References

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

- Definition

Date the credit facility terminates, in YYYY-MM-DD format.

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Balance Type:	na
Period Type:	duration

- Definition

Amount of increase (decrease) of the credit facility.

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Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
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Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Maximum amount borrowed under the credit facility at any time during the period.

+ References

No definition available.

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Balance Type:	credit
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.

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Balance Type:	credit
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- Definition

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

+ References

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- Definition

The fee, expressed as a percentage of the line of credit facility, for available but unused credit capacity under the credit facility.

+ References

No definition available.

+ Details

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- Definition

The cash inflow from a debt initially having maturity due after one year or beyond the operating cycle, if longer.

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Balance Type:	debit
Period Type:	duration

- Definition

Amount of cash outflow for payment of an obligation from a lender, including but not limited to, letter of credit, standby letter of credit and revolving credit arrangements.

+ References

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-SubTopic 10
-Name Accounting Standards Codification
-Section 45
-Paragraph 15
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147482740/230-10-45-15

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.4-08(f))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480678/235-10-S99-1

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Debt - Additional Information (Detail) $ in Thousands, $ in Millions							1 Months Ended		12 Months Ended
	Dec. 20, 2024 USD ($)	Nov. 19, 2024 USD ($) StorageFacility	Jul. 31, 2024 USD ($) StorageFacility	Mar. 12, 2024	Mar. 07, 2024 USD ($)	Feb. 22, 2024 USD ($)	Jan. 31, 2025 USD ($) StorageFacility	Dec. 31, 2024 USD ($) StorageFacility	Dec. 31, 2024 USD ($) Property	Feb. 04, 2025 USD ($)	Mar. 07, 2024 CAD ($)	Dec. 31, 2023 USD ($)	Mar. 16, 2021 USD ($)
Debt Instrument [Line Items]
Weighted average interest rate on debt								5.90%	5.90%
Initial maximum amount available													$ 500,000
Aggregate borrowings								$ 1,322,374	$ 1,322,374
Number of operating properties \| Property									93
Daily Simple SOFR Plus
Debt Instrument [Line Items]
Debt instrument, variable interest rate			3.00%
2027 Ladera Ranch Loan
Debt Instrument [Line Items]
Debt issued	$ 42,000
Aggregate borrowings								42,000	$ 42,000			$ 0
Percentage of origination fee	3.00%
Origination fee amount	$ 1,300
Maturity date	Dec. 05, 2027
Debt Instrument Fixed Rate	5.00%
2025 KeyBank Acquisition Facility
Debt Instrument [Line Items]
Initial maximum amount available		$ 175,000
Maturity date		Nov. 19, 2025
Debt instrument, fee percentage		0.20%
Line of credit facility, term of extension options		6 months
Increased the principal borrowing amount								$ 85,200
Line of credit facility, current borrowing capacity		$ 15,000
Number of self storage real estate joint ventures \| StorageFacility		1						3
2025 KeyBank Acquisition Facility \| Subsequent Event
Debt Instrument [Line Items]
Increased the principal borrowing amount							$ 74,800
Number of self storage real estate joint ventures \| StorageFacility							2
2025 KeyBank Acquisition Facility \| Maximum \| Daily Simple SOFR Loans and Term SOFR Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate		3.25%
2025 KeyBank Acquisition Facility \| Maximum \| Base Rate Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate		2.25%
2025 KeyBank Acquisition Facility \| Minimum \| Daily Simple SOFR Loans and Term SOFR Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate		2.75%
2025 KeyBank Acquisition Facility \| Minimum \| Base Rate Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate		1.75%
2025 KeyBank Acquisition Facility \| Minimum \| Key Bank
Debt Instrument [Line Items]
Non-recourse debt		$ 75,000
Initial advance under the 2025 KeyBank Acquisition Facility \| Daily Simple SOFR Loans and Term SOFR Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate		2.75%
2027 NBC Loan
Debt Instrument [Line Items]
Debt Instrument Fixed Rate				6.42%
Term				25 years
2027 NBC Loan \| CORRA Adjustment
Debt Instrument [Line Items]
Debt Instrument Fixed Rate								0.30%	0.30%
Debt instrument, variable interest rate									2.20%
KeyBank Florida CMBS Loan \| Subsequent Event
Debt Instrument [Line Items]
Initial maximum amount available										$ 700,000
Outstanding amount										51,000
Credit Facility increase commitments										$ 50,000
2025 KeyBank Bridge Loan
Debt Instrument [Line Items]
Debt issued			$ 45,000
Maturity date			Jul. 31, 2025
Acquisition Cost			$ 20,000
2025 KeyBank Bridge Loan \| Daily Simple SOFR Plus
Debt Instrument [Line Items]
Debt instrument, variable interest rate			2.75%
SSGT III
Debt Instrument [Line Items]
Number of self storage real estate joint ventures \| StorageFacility			2
SSGT III Bridge Loan
Debt Instrument [Line Items]
Debt issued			$ 20,000
Additional borrowed amount								$ 2,900	$ 2,900
SSGT III Bridge Loan \| Daily Simple SOFR Plus
Debt Instrument [Line Items]
Debt instrument, variable interest rate			3.00%
Initial Advances under 2024 Credit Facility \| Daily Simple SOFR Loans, Term SOFR Loans and CORRA Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate						1.75%
Credit Facility Revolver
Debt Instrument [Line Items]
Additional amount available under credit facility								7,300	7,300
Aggregate borrowings								614,800	$ 614,800
Credit Facility Term Loan
Debt Instrument [Line Items]
Line of credit facility, annual unused fee									2.30%
Credit facility agreement
Debt Instrument [Line Items]
Line of credit facility, annual unused fee									60.00%
Credit Facility
Debt Instrument [Line Items]
Aggregate borrowings								614,831	$ 614,831			$ 0
Increased the principal borrowing amount									94,000
Line of credit facility, current borrowing capacity								650,000	650,000
Amount borrowed under the credit facility									$ 615,000
Credit Facility \| Secured Overnight Financing Rate (SOFR) Overnight Index Swap Rate [Member]
Debt Instrument [Line Items]
Debt instrument, variable interest rate									1.85%
Credit Facility \| SOFR Index Adjustment [Member]
Debt Instrument [Line Items]
Debt instrument, variable interest rate									0.10%
Credit Facility \| Key Bank
Debt Instrument [Line Items]
Initial maximum amount available								$ 650,000	$ 650,000
Additional amount available under credit facility						$ 850,000
Maturity date						Feb. 22, 2027
Debt instrument, fee percentage						0.20%
Line of credit facility, term of extension options						1 year
Repayment of borrowings						$ 576,000
Credit Facility \| Maximum \| Base Rate Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate						1.30%
Credit Facility \| Maximum \| Daily Simple SOFR Loans, Term SOFR Loans and CORRA Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate						2.30%
Credit Facility \| Maximum \| Key Bank
Debt Instrument [Line Items]
Initial maximum amount available						$ 1,500,000
Line of credit facility, annual unused fee						0.25%
Credit Facility \| Maximum \| Key Bank \| Letter of Credit
Debt Instrument [Line Items]
Credit facility sublimits						$ 25,000
Credit Facility \| Maximum \| Key Bank \| Swingline Loans
Debt Instrument [Line Items]
Credit facility sublimits						$ 25,000
Credit Facility \| Minimum \| Base Rate Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate						0.65%
Credit Facility \| Minimum \| Daily Simple SOFR Loans, Term SOFR Loans and CORRA Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate						1.65%
Credit Facility \| Minimum \| Key Bank
Debt Instrument [Line Items]
Line of credit facility, annual unused fee						0.15%
Non-recourse debt						$ 75,000
Credit Facility \| Consolidated Leverage Ratio \| Maximum \| Base Rate Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate						1.25%
Credit Facility \| Consolidated Leverage Ratio \| Maximum \| Daily Simple SOFR Loans, Term SOFR Loans and CORRA Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate						2.25%
Credit Facility \| Consolidated Leverage Ratio \| Minimum \| Base Rate Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate						0.40%
Credit Facility \| Consolidated Leverage Ratio \| Minimum \| Daily Simple SOFR Loans, Term SOFR Loans and CORRA Loans
Debt Instrument [Line Items]
Debt instrument, variable interest rate						1.40%
Credit Facility \| 2027 NBC Loan
Debt Instrument [Line Items]
Aggregate borrowings											$ 75
Net proceeds from loan					$ 55,100
Credit Facility \| Security Interest Termination Event \| Maximum \| Key Bank
Debt Instrument [Line Items]
Capitalization rate leverage ratio						60.00%
Secured debt ratio						40.00%
Credit Facility \| Security Interest Termination Event \| Minimum \| Key Bank
Debt Instrument [Line Items]
Credit facility cross default provision amount						$ 25,000
fixed charge coverage ratio						1.5
Unsecured interest coverage ratio						2