Participation and Contributions to Multi Employer Pension Plans (Detail) - USD ($) $ in Thousands	12 Months Ended
Sep. 30, 2016	Sep. 30, 2015	Sep. 30, 2014
Multiemployer Plans [Line Items]
Partnership Contributions	$ 8,383	$ 9,218	$ 8,374
New England Teamsters & Trucking Industry Pension Fund
Multiemployer Plans [Line Items]
EIN / Pension Plan Number	04-6372430 / 001
Pension Protection Act Zone Status	Red	Red
FIP / RP Status Pending / Implemented	Implemented
Partnership Contributions	$ 2,507	$ 3,183	2,868
Surcharge Imposed	No
Westchester Teamsters Pension Fund
Multiemployer Plans [Line Items]
EIN / Pension Plan Number	13-6123973 / 001
Pension Protection Act Zone Status	Green	Green
FIP / RP Status Pending / Implemented	NA
Partnership Contributions	$ 865	$ 877	855
Surcharge Imposed	No
Local 553 Pension Fund
Multiemployer Plans [Line Items]
EIN / Pension Plan Number	13-6637826 / 001
Pension Protection Act Zone Status	Green	Green
FIP / RP Status Pending / Implemented	NA
Partnership Contributions	$ 2,645	$ 2,838	2,649
Surcharge Imposed	No
Local 463 Pension Fund
Multiemployer Plans [Line Items]
EIN / Pension Plan Number	11-1800729 / 001
Pension Protection Act Zone Status	Green	Green
FIP / RP Status Pending / Implemented	NA
Partnership Contributions	$ 148	$ 171	156
Surcharge Imposed	No
All Other Multiemployer Pension Plans
Multiemployer Plans [Line Items]
Partnership Contributions	$ 2,218	$ 2,149	$ 1,846

Entity Tax Identification Number Multiemployer Plan Number

No definition available.

Name:	sgu_EntityTaxIdentificationNumberMultiemployerPlanNumber
Namespace Prefix:	sgu_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Pension Fund Partnership Contributions

+ References

No definition available.

+ Details

Name:	sgu_PensionFundPartnershipContributions
Namespace Prefix:	sgu_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Indicate the multiemployer plan's certified zone status as currently required by the Pension Protection Act of 2006 or a subsequent amendment thereof. The zone status categories are red (critical status), orange (seriously endangered), yellow (endangered), and green (none of the above). The acceptable values are "red", "orange", "yellow", "green", "other", and "NA". A multiemployer plan is a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

+ Details

Name:	us-gaap_MultiemployerPlansCertifiedZoneStatus
Namespace Prefix:	us-gaap_
Data Type:	us-types:zoneStatusItemType
Balance Type:	na
Period Type:	duration

- Definition

Indicate whether a funding improvement plan or rehabilitation plan has been implemented or is pending for a pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. The acceptable values are "no", "pending", "implemented", "other", and "NA".

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (f)(1)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

+ Details

Name:	us-gaap_MultiemployerPlansFundingImprovementPlanAndRehabilitationPlan
Namespace Prefix:	us-gaap_
Data Type:	us-types:fundingImprovementAndRehabilitationPlanItemType
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

No definition available.

+ Details

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

- Definition

Indicate whether the employer paid a surcharge to the pension or postretirement benefit plan to which two or more unrelated employers contribute where assets contributed by one participating employer may be used to provide benefits to employees of other participating employers. The acceptable values are "no", "yes", and "NA".

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 715
-SubTopic 80
-Section 50
-Paragraph 5
-Subparagraph (f)(2)
-URI http://asc.fasb.org/extlink&oid=65877416&loc=SL14450657-114947

+ Details

Name:	us-gaap_MultiemployerPlansSurcharge
Namespace Prefix:	us-gaap_
Data Type:	us-types:surchargeItemType
Balance Type:	na
Period Type:	duration

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=us-gaap_PensionPlansDefinedBenefitMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=sgu_WestchesterTeamstersPensionFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=sgu_LocalFiveHundredAndFiftyThreePensionFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=sgu_LocalFourHundredAndSixtyThreePensionFundMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_DefinedBenefitPlansDisclosuresDefinedBenefitPlansAxis=sgu_AllOtherMultiemployerPensionPlansMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: