Increase (Decrease) Of Intangible Assets Impairment

No definition available.

Name:	lscc_IncreaseDecreaseOfIntangibleAssetsImpairment
Namespace Prefix:	lscc_
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- 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_FiniteLivedIntangibleAssetsLineItems
Namespace Prefix:	us-gaap_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount of increase (decrease) in carrying value of assets, excluding financial assets and goodwill, lacking physical substance with a finite life.

+ References

No definition available.

+ Details

Name:	us-gaap_FiniteLivedIntangibleAssetsPeriodIncreaseDecrease
Namespace Prefix:	us-gaap_
Data Type:	xbrli:monetaryItemType
Balance Type:	na
Period Type:	duration

- Definition

The amount of impairment loss recognized in the period resulting from the write-down of the carrying amount of a finite-lived intangible asset to fair value.

+ References

Reference 1: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 28
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2009/role/commonPracticeRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 350
-SubTopic 30
-Section 50
-Paragraph 3
-Subparagraph (b)
-URI http://asc.fasb.org/extlink&oid=66006027&loc=d3e16373-109275

+ Details

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

- Definition

The cash inflow from disposal of asset without physical form usually arising from contractual or other legal rights, excluding goodwill.

+ References

Reference 1: http://fasb.org/us-gaap/role/ref/legacyRef
-Publisher FASB
-Name Accounting Standards Codification
-Topic 230
-SubTopic 10
-Section 45
-Paragraph 12
-Subparagraph (c)
-URI http://asc.fasb.org/extlink&oid=109223946&loc=d3e3179-108585

+ Details

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

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_DevelopedTechnologyRightsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_CustomerRelationshipsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_FiniteLivedIntangibleAssetsByMajorClassAxis=us-gaap_PatentsMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_BusinessAcquisitionAxis=lscc_SiliconImageIncMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Intangible Assets - Additional Information (Details) - USD ($) $ in Thousands	3 Months Ended					12 Months Ended
	Sep. 29, 2018	Jun. 30, 2018	Sep. 30, 2017	Apr. 01, 2017	Oct. 01, 2016	Dec. 29, 2018	Dec. 30, 2017	Dec. 31, 2016
Finite-Lived Intangible Assets [Line Items]
Impairment of acquired intangible assets	$ 600	$ 11,900			$ 7,900	$ 12,486	$ 32,431	$ 7,866
Developed technology
Finite-Lived Intangible Assets [Line Items]
Impairment of acquired intangible assets						12,486	32,431
Customer relationships
Finite-Lived Intangible Assets [Line Items]
Impairment of acquired intangible assets						$ 0	0
Patents
Finite-Lived Intangible Assets [Line Items]
Proceeds from sale of intangible assets				$ 18,000
Decrease of intangible assets							3,500
Silicon Image, Inc \| Developed technology
Finite-Lived Intangible Assets [Line Items]
Impairment of acquired intangible assets			$ 36,200				$ 32,400
Reduction to preliminary impairment charge			$ 3,800