Basis of Presentation - Additional Information (Detail)	3 Months Ended
Mar. 31, 2013
Basis Of Presentation [Abstract]
Number of weeks in a quarter for financial reporting purposes	13-or 14-week quarter

Number of weeks in quarter for financial reporting purposes

No definition available.

Name:	lsi_NumberOfWeeksInQuarterForFinancialReportingPurposes
Namespace Prefix:	lsi_
Data Type:	xbrli:stringItemType
Balance Type:	na
Period Type:	duration