Subsequent Events (Details) - Line of Credit - 2018 Credit Agreement - Subsequent Event	Aug. 08, 2018 USD ($)
Subsequent Event [Line Items]
Fixed charge coverage ratio	1.1
Percent availability under revolving commitment	12.50%
Percentage of stock pledged on credit agreement	66.67%
Revolving credit agreement
Subsequent Event [Line Items]
Revolving credit facility, maximum borrowing capacity	$ 30,000,000
Accordion feature, increase limit	$ 10,000,000

Line Of Credit Facility, Accordion Feature, Increase Limit

No definition available.

Name:	sif_LineOfCreditFacilityAccordionFeatureIncreaseLimit
Namespace Prefix:	sif_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Line Of Credit Facility, Availability Of Revolving Commitment, Fixed Charge Coverage Ratio Threshold

+ References

No definition available.

+ Details

Name:	sif_LineOfCreditFacilityAvailabilityOfRevolvingCommitmentFixedChargeCoverageRatioThreshold
Namespace Prefix:	sif_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Line of Credit Facility, Covenant Terms, Fixed Charge Coverage Ratio

+ References

No definition available.

+ Details

Name:	sif_LineofCreditFacilityCovenantTermsFixedChargeCoverageRatio
Namespace Prefix:	sif_
Data Type:	xbrli:pureItemType
Balance Type:	na
Period Type:	instant

- Definition

Line of Credit Facility, Stock Pledged, Non-U.S. Subsidiaries, Percentage

+ References

No definition available.

+ Details

Name:	sif_LineofCreditFacilityStockPledgedNonU.S.SubsidiariesPercentage
Namespace Prefix:	sif_
Data Type:	num: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
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.19(b),22(b))
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

Detail information of subsequent event by type. User is expected to use existing line items from elsewhere in the taxonomy as the primary line items for this disclosure, which is further associated with dimension and member elements pertaining to a subsequent event.

+ References

No definition available.

+ Details

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

- Details

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

- Details

Name:	us-gaap_DebtInstrumentAxis=sif_A2018CreditAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_SubsequentEventTypeAxis=us-gaap_SubsequentEventMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

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