The consideration received in connection with the license agreement and collaborative arrangement.

No definition available.

Name:	sigm_CollaborativeArrangementConsiderationReceived
Namespace Prefix:	sigm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the percentage of net profit receivable by the company as marketing service fee under collaborative arrangement.

+ References

No definition available.

+ Details

Name:	sigm_CollaborativeArrangementPercentageOfNetProfitReceivableAsMarketingServiceFee
Namespace Prefix:	sigm_
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	duration

- Definition

Represents the reimbursement of prior payments for a mask set associated with the collaborative arrangement.

+ References

No definition available.

+ Details

Name:	sigm_CollaborativeArrangementReimbursementOfPriorPayments
Namespace Prefix:	sigm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Upon milestone satisfaction, the remaining amount receivable from a counter party related to a collaborative arrangement.

+ References

No definition available.

+ Details

Name:	sigm_CollaborativeArrangementRemainingPayment
Namespace Prefix:	sigm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of cumulative amortization expense reversed during the period.

+ References

No definition available.

+ Details

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

- Definition

The amount of cumulative net losses reversed during the period.

+ References

No definition available.

+ Details

Name:	sigm_CumulativeNetLossesReversed
Namespace Prefix:	sigm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

The amount of cumulative share of research and development expense reversed during the period.

+ References

No definition available.

+ Details

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

- Definition

The amount of net loss from a collaborative arrangement.

+ References

No definition available.

+ Details

Name:	sigm_NetLossFromCollaborativeArrangement
Namespace Prefix:	sigm_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of accumulated depreciation, depletion and amortization for physical assets used in the normal conduct of business to produce goods and services.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 360
-SubTopic 10
-Section 50
-Paragraph 1
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=6391035&loc=d3e2868-110229

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 210
-SubTopic 10
-Section S99
-Paragraph 1
-Subparagraph (SX 210.5-02.14)
-URI http://asc.fasb.org/extlink&oid=6877327&loc=d3e13212-122682

+ Details

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

- Definition

The aggregate costs incurred (1) in a planned search or critical investigation aimed at discovery of new knowledge with the hope that such knowledge will be useful in developing a new product or service, a new process or technique, or in bringing about a significant improvement to an existing product or process; or (2) to translate research findings or other knowledge into a plan or design for a new product or process or for a significant improvement to an existing product or process whether intended for sale or the entity's use, during the reporting period charged to research and development projects, including the costs of developing computer software up to the point in time of achieving technological feasibility, and costs allocated in accounting for a business combination to in-process projects deemed to have no alternative future use.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 985
-SubTopic 20
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6501960&loc=d3e128462-111756

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 730
-SubTopic 10
-Section 50
-Paragraph 1
-URI http://asc.fasb.org/extlink&oid=6420194&loc=d3e21568-108373

+ Details

Name:	us-gaap_ResearchAndDevelopmentExpense
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Amount of revenue recognized from goods sold, services rendered, insurance premiums, or other activities that constitute an earning process. Includes, but is not limited to, investment and interest income before deduction of interest expense when recognized as a component of revenue, and sales and trading gain (loss).

+ References

Reference 1: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

Reference 2: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 220
-SubTopic 10
-Section S99
-Paragraph 2
-Subparagraph (SX 210.5-03.1)
-URI http://asc.fasb.org/extlink&oid=115205541&loc=SL114868664-224227

Reference 3: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 32
-Subparagraph (a)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8933-108599

Reference 4: http://www.xbrl.org/2003/role/disclosureRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 280
-SubTopic 10
-Section 50
-Paragraph 22
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=115929826&loc=d3e8736-108599

+ Details

Name:	us-gaap_Revenues
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Details

Name:	srt_CounterpartyNameAxis=sigm_TelechipsIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_PropertyPlantAndEquipmentByTypeAxis=sigm_MaskSetsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=us-gaap_CollaborativeArrangementProductAgreementMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_TypeOfArrangementAxis=sigm_CollaborativeArrangementMaskSetMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	srt_ProductOrServiceAxis=us-gaap_LicenseMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Note 13 - Collaborative Arrangement (Details Textual) - USD ($) $ in Thousands		1 Months Ended	3 Months Ended		9 Months Ended
	Aug. 14, 2017	Sep. 30, 2016	Oct. 28, 2017	Apr. 29, 2017	Oct. 28, 2017	May 05, 2018	Feb. 03, 2018
Research and Development Expense, Total				$ 18,169
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance						$ 35,239	$ 70,524
Revenues, Total				39,564
Telechips Inc [Member] \| Mask Sets [Member]
Accumulated Depreciation, Depletion and Amortization, Property, Plant, and Equipment, Ending Balance	$ 600
Collaborative Arrangement, Product [Member] \| Telechips Inc [Member]
Collaborative Arrangement, Percentage of Net Profit Receivable as Marketing Service Fee		50.00%
Net Loss from Collaborative Arrangement				100
Research and Development Expense, Total				$ 500
Collaborative Arrangement, Reimbursement of Prior Payments	2,500
Collaborative Arrangement, Mask Set [Member] \| Telechips Inc [Member]
Collaborative Arrangement, Consideration Received	$ 4,700
Collaborative Arrangement, Remaining Payment			$ 1,100
Cumulative Amortization Expense, Reversed			600
Cumulative Share of Research and Development Expense, Reversed			700
Cumulative Net Income (Losses), Reversed					$ (300)
Collaborative Arrangement, Mask Set [Member] \| Telechips Inc [Member] \| License [Member]
Revenues, Total			$ 1,100