Debt Instrument, Agent Fee

No definition available.

Name:	suns_DebtInstrumentAgentFee
Namespace Prefix:	suns_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Line Of Credit Facility, Accordion Feature, Increase Limit

+ References

No definition available.

+ Details

Name:	suns_LineOfCreditFacilityAccordionFeatureIncreaseLimit
Namespace Prefix:	suns_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of Credit Facility, Commencement of Payment of Unused Capacity, Commitment Fee Percentage

+ References

No definition available.

+ Details

Name:	suns_LineOfCreditFacilityCommencementOfPaymentOfUnusedCapacityCommitmentFeePercentage
Namespace Prefix:	suns_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of Credit Facility, Covenant, Leverage Ratio, Maximum

+ References

No definition available.

+ Details

Name:	suns_LineOfCreditFacilityCovenantLeverageRatioMaximum
Namespace Prefix:	suns_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Line of Credit Facility, Covenant, Quarterly Debt Service Coverage Ratio, Minimum

+ References

No definition available.

+ Details

Name:	suns_LineOfCreditFacilityCovenantQuarterlyDebtServiceCoverageRatioMinimum
Namespace Prefix:	suns_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Line Of Credit Facility, Liquidity Covenant, Minimum, Amount

+ References

No definition available.

+ Details

Name:	suns_LineOfCreditFacilityLiquidityCovenantMinimumAmount
Namespace Prefix:	suns_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Line Of Credit Facility, Liquidity Covenant, Outstanding Obligations, Percent

+ References

No definition available.

+ Details

Name:	suns_LineOfCreditFacilityLiquidityCovenantOutstandingObligationsPercent
Namespace Prefix:	suns_
Data Type:	dtr-types:percentItemType
Balance Type:	na
Period Type:	instant

- 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

Incremental percentage increase (decrease) in the stated rate on a debt instrument.

+ References

No definition available.

+ Details

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

- 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

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22))
-SubTopic 10
-Topic 210
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 942
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.9-03(16))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478546/942-210-S99-1

Reference 3: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 944
-SubTopic 210
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.7-03(a)(16)(a)(2))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147478777/944-210-S99-1

+ Details

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

- Definition

Amount of the fee for available but unused credit capacity under the credit facility.

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 3: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

Name:	us-gaap_LineOfCreditFacilityCommitmentFeeAmount
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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

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

- Definition

The effective interest rate during the reporting period.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(22)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Topic 210
-SubTopic 10
-Name Accounting Standards Codification
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02(19)(b))
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480566/210-10-S99-1

+ Details

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

- 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

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 235
-SubTopic 10
-Name Accounting Standards Codification
-Section S50
-Paragraph 1
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147480738/235-10-S50-1

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

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (b)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

Reference 4: http://www.xbrl.org/2009/role/commonPracticeRef
-Topic 470
-SubTopic 10
-Name Accounting Standards Codification
-Section 50
-Paragraph 6
-Subparagraph (a)
-Publisher FASB
-URI https://asc.fasb.org/1943274/2147481544/470-10-50-6

+ Details

Name:	us-gaap_LineOfCreditFacilityLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
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

+ 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

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

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

- Definition

The remaining balance of debt issuance expenses that were capitalized and are being amortized against income over the lives of the respective bond issues. This does not include the amounts capitalized as part of the cost of the utility plant or asset.

+ References

No definition available.

+ Details

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

- Details

Name:	us-gaap_CreditFacilityAxis=us-gaap_RevolvingCreditFacilityMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_SecuredDebtMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=suns_RevolvingCreditFacilityOtherMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_SecuredOvernightFinancingRateSofrMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_VariableRateAxis=us-gaap_BaseRateMember
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Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_LongtermDebtTypeAxis=us-gaap_UnsecuredDebtMember
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Period Type:

- Details

Name:	us-gaap_DebtInstrumentAxis=suns_SRTFRevolvingCreditFacilityMember
Namespace Prefix:
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DEBT - Narrative (Details) - Revolving Credit Facility - USD ($)				3 Months Ended		9 Months Ended		12 Months Ended
	Dec. 09, 2024	Nov. 06, 2024	Sep. 26, 2024	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024	Dec. 31, 2024
Line of Credit Facility [Line Items]
Unused fee expense				$ 45,577	$ 0	$ 67,490	$ 0
Secured Debt
Line of Credit Facility [Line Items]
Agent fee		$ 75,000
Loan fee payable (as a percent)		0.25%
Commencement of unused capacity, commitment fee percentage payable (in months)		6 months
Unused line fee (as a percent)		0.25%
Unused fee expense				$ 45,600		67,500
Unamortized debt issuance expense		$ 500,000
Minimum liquidity covenant						$ 5,000,000
Outstanding obligations (as a percent)				10.00%		10.00%
Quarterly debt service coverage ratio				1.50		1.50
Maximum leverage ratio				3.25		3.25
Secured Debt \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit loan commitment		50,000,000		$ 140,000,000		$ 140,000,000
Increase limit		$ 200,000,000
Increase in interest rate (as a percent)		0.25%
Unused fee expense				45,577	0	67,490	0
Line of credit				67,200,000		67,200,000		$ 123,800,000
Line of credit, available to borrow				72,800,000		$ 72,800,000		$ 1,200,000
Line of credit facility, interest rate (as a percent)						7.02%		7.28%
Secured Debt \| Secured Overnight Financing Rate (SOFR) \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Basis spread on variable interest rate (as a percent)		2.75%
Secured Debt \| Base Rate \| Revolving Credit Facility
Line of Credit Facility [Line Items]
Basis spread on variable interest rate (as a percent)		2.63%
Unsecured Debt \| SRTF Revolving Credit Facility
Line of Credit Facility [Line Items]
Revolving credit loan commitment	$ 75,000,000		$ 50,000,000
Loan fee payable (as a percent)	1.00%
Unused fee expense				0	$ 0	$ 0	$ 0
Unamortized debt issuance expense	$ 20,000.0
Line of credit				0		0		$ 75,000,000.0
Line of credit, available to borrow				$ 75,000,000.0		$ 75,000,000.0		$ 0
Line of credit facility, interest rate (as a percent)						8.00%
Unsecured Debt \| Secured Overnight Financing Rate (SOFR) \| SRTF Revolving Credit Facility
Line of Credit Facility [Line Items]
Basis spread on variable interest rate (as a percent)			3.00%
Unsecured Debt \| Base Rate \| SRTF Revolving Credit Facility
Line of Credit Facility [Line Items]
Basis spread on variable interest rate (as a percent)			2.75%