Commitments, Contingencies and Legal Matters (Details) (USD $)	1 Months Ended	9 Months Ended
Feb. 28, 2009	Oct. 02, 2011	Dec. 31, 2010
Summary of changes in product warranties
Balance as of December 31, 2010		$ 17,617,000
Accruals for warranties issued during the period		6,382,000
Accruals related to pre-existing warranties (including changes in estimates)		500,000
Settlements made during the period (in cash or in kind)		(5,983,000)
Balance as of October 2, 2011		18,516,000
Commitments, Contingencies and Legal Matters (Textuals) [Abstract]
Total purchase commitments due through 2016		390,600,000
Company's percentage of take-or-pay agreement with SMP		51.00%
Terms in which take-or-pay agreement may be terminated by either party		Upon two years written notice
Warranty period for finished goods against defects in material and workmanship under normal use and service		one to three years
Jury award to GE for patent infringement	7,600,000
Outstanding obligation related to standby letters of credit		$ 2,900,000	$ 3,900,000

Commitments contingencies and legal matters.

Name:	lsi_CommitmentsContingenciesAndLegalMattersTextualsAbstract
Namespace Prefix:	lsi
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Company's percentage of take-or-pay agreement.

+ Details

Name:	lsi_CompanysPercentageOfTakeOrPayAgreement
Namespace Prefix:	lsi
Data Type:	num:percentItemType
Balance Type:	na
Period Type:	instant

- Definition

Outstanding obligations related to standby letters of credit.

+ Details

Name:	lsi_OutstandingObligationsRelatedToStandbyLettersOfCredit
Namespace Prefix:	lsi
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Short-term and long-term purchase commitments.

+ Details

Name:	lsi_ShortTermAndLongTermPurchaseCommitments
Namespace Prefix:	lsi
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Terms in which take or pay agreement may be terminated by either party.

+ Details

Name:	lsi_TermsInWhichTakeOrPayAgreementMayBeTerminatedByEitherParty
Namespace Prefix:	lsi
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

This element represents the gross amount awarded, to be received by, or to be remitted to the entity in settlement of litigation occurring during the period.

+ Details

Name:	us-gaap_LitigationSettlementGross
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

A roll forward is a reconciliation of a concept from the beginning of a period to the end of a period.

+ Details

Name:	us-gaap_MovementInStandardProductWarrantyAccrualRollForward
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration

- Definition

Amount as of the balance sheet date of the aggregate standard product warranty liability. Does not include the balance for the extended product warranty liability.

+ References

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 14

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (c)(1),(c)(5)

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

+ Details

Name:	us-gaap_StandardProductWarrantyAccrual
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	instant

- Definition

Represents the aggregate decrease in the liability for payments made (in cash or in kind) to satisfy claims under the terms of the standard product warranty. Does not include any Increase or Decrease in the liability for payments related to extended product warranties.

+ References

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 14

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph ((c)(2))

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

+ Details

Name:	us-gaap_StandardProductWarrantyAccrualPayments
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	debit
Period Type:	duration

- Definition

Represents the aggregate Increase or Decrease in the liability during the reporting period for accruals related to preexisting standard product warranties (including adjustments related to changes in estimates). Does not include any Increase or Decrease in the liability for accruals related to extended product warranties.

+ References

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 14

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph ((c)(4))

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

+ Details

Name:	us-gaap_StandardProductWarrantyAccrualPreexistingIncreaseDecrease
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Represents the aggregate increase in the liability for accruals related to standard product warranties issued during the reporting period. Does not include any increase in the liability for accruals related to extended product warranties.

+ References

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 14

-Subparagraph b

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph ((c)(3))

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

+ Details

Name:	us-gaap_StandardProductWarrantyAccrualWarrantiesIssued
Namespace Prefix:	us-gaap
Data Type:	xbrli:monetaryItemType
Balance Type:	credit
Period Type:	duration

- Definition

Describes the nature of the product warranty, including the approximate term of the product warranty, how the product warranty arose, and the events or circumstances that would require the warrantor to perform under the product warranty.

+ References

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

-Publisher FASB

-Name FASB Interpretation (FIN)

-Number 45

-Paragraph 13

-Subparagraph a

-LegacyDoc This reference is SUPERSEDED by the Accounting Standards Codification effective for interim and annual periods ending after September 15, 2009. This reference is included to help users transition from the previous accounting hierarchy and will be removed from future versions of this taxonomy.

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 4

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6851643&loc=d3e12069-110248

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

-Publisher FASB

-Name Accounting Standards Codification

-Topic 460

-SubTopic 10

-Section 50

-Paragraph 8

-Subparagraph (a)

-URI http://asc.fasb.org/extlink&oid=6398077&loc=d3e12565-110249

+ Details

Name:	us-gaap_StandardProductWarrantyDescription
Namespace Prefix:	us-gaap
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration