CREDIT FACILITIES (Details)	12 Months Ended
Dec. 31, 2020 USD ($) financial_institution
Line of Credit Facility [Line Items]
Restricted cash collateralizing letters of credit outstanding	$ 1,600,000
Revolving Credit Facility
Line of Credit Facility [Line Items]
Maximum borrowing capacity	$ 75,000,000
Number of financial institutions \| financial_institution	1
Term of credit facility	5 years
Percentage of inventory advance rate computed	60.00%
Percentage of inventory advance rate of net orderly liquidation value	85.00%
Eligible collateral under the credit facility	$ 75,000,000.0
Total availability and excess availability under the credit facility	72,600,000
Outstanding borrowings	$ 0
Revolving Credit Facility \| Maximum
Line of Credit Facility [Line Items]
Percentage of eligible accounts receivable for borrowings	85.00%

Refers to the amount of eligible collateral letters of credit, based on borrowing base availability.

No definition available.

Name:	syx_EligibleCollateralUnderTheCreditFacility
Namespace Prefix:	syx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Number Of Financial Institutions

+ References

No definition available.

+ Details

Name:	syx_NumberOfFinancialInstitutions
Namespace Prefix:	syx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	duration

- Definition

Refers to the amount of outstanding advances.

+ References

No definition available.

+ Details

Name:	syx_OutstandingAdvances
Namespace Prefix:	syx_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

The percentage of eligible accounts receivable for borrowings under the agreement.

+ References

No definition available.

+ Details

Name:	syx_PercentageOfEligibleAccountsReceivableForBorrowings
Namespace Prefix:	syx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Refers to percentage of inventory advance rate computed as the lesser of NOVL (Net Orderly Liquidation Value).

+ References

No definition available.

+ Details

Name:	syx_PercentageOfInventoryAdvanceRateComputed
Namespace Prefix:	syx_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Refers to percentage of inventory advance rate computed of NOVL (Net Orderly Liquidation Value).

+ References

No definition available.

+ Details

Name:	syx_PercentageOfInventoryAdvanceRateOfNOVL
Namespace Prefix:	syx_
Data Type:	num:percentItemType
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

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

- Definition

The total amount of the contingent obligation under letters of credit outstanding as of the reporting date.

+ References

No definition available.

+ Details

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

- 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

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=120391452&loc=d3e13212-122682

+ Details

Name:	us-gaap_LineOfCreditFacilityCurrentBorrowingCapacity
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
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_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

- Details

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

- Details

Name:	srt_RangeAxis=srt_MaximumMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type: