Amount of cash payments made as the result of exit or disposal activities. Excludes payments associated with a discontinued operation or an asset retirement obligation.

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

- Definition

Discloses the amount charged against the accrued restructuring reserves, or earnings if not previously accrued, during the period for the specified type of restructuring cost.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

+ Details

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

- Definition

The number of positions eliminated as of the balance sheet date since inception of the restructuring plan(s).

+ References

No definition available.

+ Details

Name:	us-gaap_RestructuringAndRelatedCostNumberOfPositionsEliminatedInceptionToDate
Namespace Prefix:	us-gaap_
Data Type:	xbrli:integerItemType
Balance Type:	na
Period Type:	instant

- Definition

Amount of expenses associated with exit or disposal activities pursuant to an authorized plan. Excludes expenses related to a discontinued operation or an asset retirement obligation.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 230

-SubTopic 10

-Section 45

-Paragraph 28

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=31042434&loc=d3e3602-108585

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section 50

-Paragraph 1

-Subparagraph (b)

-URI http://asc.fasb.org/extlink&oid=6394359&loc=d3e17939-110869

Reference 3: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 4: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 1

-Subparagraph (SAB TOPIC 5.P.3)

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140864-122747

Reference 5: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

+ Details

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

- Details

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

- Definition

Carrying amount (including both current and noncurrent portions of the accrual) as of the balance sheet date pertaining to a specified type of cost associated with exit from or disposal of business activities or restructuring pursuant to a duly authorized plan.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher FASB

-Name Accounting Standards Codification

-Topic 420

-SubTopic 10

-Section S99

-Paragraph 2

-Subparagraph (SAB TOPIC 5.P.4(b))

-URI http://asc.fasb.org/extlink&oid=27011515&loc=d3e140904-122747

Reference 2: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Staff Accounting Bulletin (SAB)

-Number Topic 5

-Section P

-Subsection 3, 4

+ Details

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

- Definition

Amount of any reversal and other adjustment made during the period to the amount of a previously accrued liability for a specified type of restructuring cost, excluding adjustments for costs incurred during the period, costs settled during the period, and foreign currency translation adjustments.

+ References

+ Details

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

- Details

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

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=lscc_LeaseLossReserveMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=us-gaap_EmployeeSeveranceMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringCostAndReserveAxis=us-gaap_OtherRestructuringMember
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringPlanAxis=lscc_RestructuringPlan2011Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

- Details

Name:	us-gaap_RestructuringPlanAxis=lscc_RestructuringPlan2012Member
Namespace Prefix:
Data Type:	na
Balance Type:
Period Type:

Restructuring (Details) (USD $) In Thousands, unless otherwise specified	3 Months Ended								12 Months Ended			3 Months Ended	6 Months Ended
	Jan. 03, 2015	Sep. 27, 2014	Jun. 28, 2014	Mar. 29, 2014	Dec. 28, 2013	Sep. 28, 2013	Jun. 29, 2013	Mar. 30, 2013	Jan. 03, 2015	Dec. 28, 2013	Dec. 29, 2012	Dec. 29, 2012	Jun. 30, 2012	Oct. 31, 2012 employee
Restructuring Cost and Reserve [Line Items]
Restructuring charges	$ 1	$ 2	$ 3	$ 11	$ 131	$ 85	$ 19	$ 153	$ 17	$ 388	$ 6,018
Restructuring Reserve [Roll Forward]
Beginning Balance				532us-gaap_RestructuringReserve				3,424us-gaap_RestructuringReserve	532us-gaap_RestructuringReserve	3,424us-gaap_RestructuringReserve	1,582us-gaap_RestructuringReserve		1,582us-gaap_RestructuringReserve
Restructuring charges									10us-gaap_RestructuringCharges	586us-gaap_RestructuringCharges	6,136us-gaap_RestructuringCharges
Cash payments									(367)us-gaap_PaymentsForRestructuring	(3,280)us-gaap_PaymentsForRestructuring	(4,176)us-gaap_PaymentsForRestructuring
Adjustments to prior restructuring costs									7	(198)	(118)
Ending Balance	182us-gaap_RestructuringReserve				532us-gaap_RestructuringReserve				182us-gaap_RestructuringReserve	532us-gaap_RestructuringReserve	3,424us-gaap_RestructuringReserve	3,424us-gaap_RestructuringReserve
Severance and related
Restructuring Reserve [Roll Forward]
Beginning Balance				17				2,373	17	2,373	1,556		1,556
Restructuring charges									0	109	4,277
Cash payments									(8)	(2,315)	(3,356)
Adjustments to prior restructuring costs									(9)	(150)	(104)
Ending Balance	0				17				0	17	2,373	2,373
Lease termination
Restructuring Reserve [Roll Forward]
Beginning Balance				368				793	368	793	26		26
Restructuring charges									1	224	1,083
Cash payments									(341)	(740)	(302)
Adjustments to prior restructuring costs									15	91	(14)
Ending Balance	43				368				43	368	793	793
Other
Restructuring Reserve [Roll Forward]
Beginning Balance				147				258	147	258	0		0
Restructuring charges									9	253	776
Cash payments									(18)	(225)	(518)
Adjustments to prior restructuring costs									1	(139)	0
Ending Balance	139				147				139	147	258	258
2012 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Approximate reduction in headcount														110
Restructuring charges												5,400
2011 Restructuring Plan
Restructuring Cost and Reserve [Line Items]
Restructuring charges													$ 700