Partnership's Debt (Parenthetical) (Detail) - Third Amendment - USD ($)	Jul. 30, 2015	Sep. 30, 2016
Debt Instrument [Line Items]
Non Seasonal maximum borrowing capacity under revolving credit facility	$ 300,000,000
Maximum borrowing capacity (heating season December to April) under revolving credit facility	450,000,000
Issuance of line of credit for working capital purposes	$ 100,000,000
Revolving credit facility expiry	Jul. 30, 2020
Additional revolving credit	$ 100,000,000
Facility size that can be increased without consulting bank group	$ 100,000,000
Term loan annual payment percentage	25.00%
Debt instrument, effective interest rate		3.62%
Minimum fixed charge coverage ratio	110.00%
Availability percentage to maximum facility size	12.50%
December through April
Debt Instrument [Line Items]
Commitment fee on the unused portion of the facility	0.30%
May through November
Debt Instrument [Line Items]
Commitment fee on the unused portion of the facility	0.20%
Maximum \| Quarters ending June or September
Debt Instrument [Line Items]
Senior secured leverage ratio	300.00%
Maximum \| Quarters ending December or March
Debt Instrument [Line Items]
Senior secured leverage ratio	450.00%
Quarterly
Debt Instrument [Line Items]
Term loan periodic payment	$ 2,500,000
Annually \| Maximum
Debt Instrument [Line Items]
Term loan periodic payment	15,000,000
$100 million Term Loan
Debt Instrument [Line Items]
Outstanding senior notes	$ 100,000,000
Senior secured term loan maturity period	5 years

Additional Annual Payment to Term Loan Facility, Percentage of Excess Cash Flow

No definition available.

Name:	sgu_AdditionalAnnualPaymentToTermLoanFacilityPercentageOfExcessCashFlow
Namespace Prefix:	sgu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Availability percentage to maximum facility size.

+ References

No definition available.

+ Details

Name:	sgu_AvailabilityPercentageToMaximumFacilitySize
Namespace Prefix:	sgu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Debt Instrument Leverage Ratio

+ References

No definition available.

+ Details

Name:	sgu_DebtInstrumentLeverageRatio
Namespace Prefix:	sgu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Line Of Credit Facility Additional Borrowing Capacity For Working Capital Needs

+ References

No definition available.

+ Details

Name:	sgu_LineOfCreditFacilityAdditionalBorrowingCapacityForWorkingCapitalNeeds
Namespace Prefix:	sgu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Facility Increase Additional Borrowing Capacity

+ References

No definition available.

+ Details

Name:	sgu_LineOfCreditFacilityIncreaseAdditionalBorrowingCapacity
Namespace Prefix:	sgu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line of credit facility maximum borrowing capacity during the heating season.

+ References

No definition available.

+ Details

Name:	sgu_LineOfCreditFacilityMaximumBorrowingCapacityDuringHeatingSeason
Namespace Prefix:	sgu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Maximum increase allowed without bank consulting.

+ References

No definition available.

+ Details

Name:	sgu_MaximumIncreaseAllowedWithoutBankConsulting
Namespace Prefix:	sgu_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Minimum Fixed Charge Coverage Ratio On Revolving Credit Facilities

+ References

No definition available.

+ Details

Name:	sgu_MinimumFixedChargeCoverageRatioOnRevolvingCreditFacilities
Namespace Prefix:	sgu_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 55
-Paragraph 8
-URI http://asc.fasb.org/extlink&oid=64930739&loc=d3e28878-108400

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ 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

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.22(a)(1))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

Reference 2: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 835
-SubTopic 30
-Section 45
-Paragraph 2
-URI http://asc.fasb.org/extlink&oid=64930785&loc=d3e28551-108399

+ Details

Name:	us-gaap_DebtInstrumentInterestRateEffectivePercentage
Namespace Prefix:	us-gaap_
Data Type:	num: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

No definition available.

+ Details

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

- Definition

Amount of the required periodic payments applied to principal.

+ References

+ Details

Name:	us-gaap_DebtInstrumentPeriodicPaymentPrincipal
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
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

Name:	us-gaap_DebtInstrumentTerm
Namespace Prefix:	us-gaap_
Data Type:	xbrli:durationItemType
Balance Type:	na
Period Type:	duration

- Definition

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

+ References

+ Details

Name:	us-gaap_LineOfCreditFacilityExpirationDate1
Namespace Prefix:	us-gaap_
Data Type:	xbrli:dateItemType
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

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:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_LineOfCreditFacilityAxis=sgu_ThirdAmendmentMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	sgu_PeriodAxis=sgu_PeriodOneMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	sgu_PeriodAxis=sgu_PeriodTwoMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RangeAxis=us-gaap_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	sgu_PeriodAxis=sgu_PeriodThreeMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	sgu_PeriodAxis=sgu_PeriodFourMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=sgu_QuarterlyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DebtInstrumentRedemptionPeriodAxis=sgu_AnnuallyMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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