COMMITMENTS, CONTINGENCIES AND OTHER MATTERS - Narrative (Details)	Dec. 31, 2020 state
Commitments and Contingencies Disclosure [Abstract]
Number of states seeking recovery of unclaimed property	28
Number of states requesting payments of claimed amounts	20

The number of states being audited and seeking recovery of unclaimed property.

No definition available.

Name:	syx_NumberOfStatesSeekingRecoveryOfUnclaimedProperty
Namespace Prefix:	syx_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant