Note 2 - Amortized Cost and Estimated Fair Value of Cash Equivalents and Marketable Securities by Maturity (Details) (USD $) In Thousands, unless otherwise specified	Nov. 01, 2014	Feb. 01, 2014
Book Value	$ 27,083	$ 36,498
Fair Value	27,276	36,817
Due in Greater Than One Year [Member]
Book Value	4,101	15,214
Fair Value	4,265	15,505
Due in One Year or Less [Member]
Book Value	22,982	21,284
Fair Value	$ 23,011	$ 21,312

Amount of (1) short-term, highly liquid investments that are both readily convertible to known amounts of cash and so near their maturity that they present insignificant risk of changes in value because of changes in interest rates; and (2) debt and equity financial instruments including: (i) securities held-to-maturity, (ii) trading securities, and (iii) securities available-for-sale.

No definition available.

Name:	sigm_CashEquivalentsAndMarketableSecurities
Namespace Prefix:	sigm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	instant