Note 5 - Supplemental Financial Information - Accrued Rebate Activity (Details) $ in Thousands	3 Months Ended
Apr. 29, 2017 USD ($)
Beginning balance	$ 1,585
Charged as a reduction of revenue	725
Payments	(458)
Ending balance	$ 1,852

Represents the aggregate increase in the liability for accrued rebates for rebates charged as a reduction of revenue.

No definition available.

Name:	sigm_AccruedRebatesChargedAsAReductionOfRevenue
Namespace Prefix:	sigm_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration