Annual report pursuant to Section 13 and 15(d)

Stock Compensation Plans - Additional Information (Details)

v2.4.1.9
Stock Compensation Plans - Additional Information (Details) (USD $)
In Thousands, except Share data, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Dec. 31, 2011
Sep. 30, 2010
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Issuance of common stock $ 3,282us-gaap_ProceedsFromIssuanceOfCommonStock $ 1,256us-gaap_ProceedsFromIssuanceOfCommonStock $ 795us-gaap_ProceedsFromIssuanceOfCommonStock    
Total compensation cost not yet recognized, stock options 11,059us-gaap_EmployeeServiceShareBasedCompensationNonvestedAwardsTotalCompensationCostNotYetRecognizedStockOptions        
Unrecognized compensation cost for stock based compensation, period of recognition 1 year 9 months 7 days        
Options, exercises in period, total intrinsic value 4,640us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 957us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue 1,267us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsExercisesInPeriodTotalIntrinsicValue    
Allocated share-based compensation expense 10,539us-gaap_AllocatedShareBasedCompensationExpense 6,766us-gaap_AllocatedShareBasedCompensationExpense 4,690us-gaap_AllocatedShareBasedCompensationExpense    
Options, outstanding, number 4,415,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 4,425,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber 4,475,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber    
Qualified Employee Stock Purchase Plan [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares available for grant 10,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
       
Offering date 5.00%us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardDiscountFromMarketPriceOfferingDate
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
       
Stock issued during period, gross 89,581us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
112,646us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
98,513us-gaap_StockIssuedDuringPeriodSharesShareBasedCompensationGross
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
   
Shares authorized under stock option plans, exercise price range, lower range limit $ 2.87us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
$ 1.57us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
$ 1.25us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeLowerRangeLimit
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
   
Shares authorized under stock option plans, exercise price range, upper range limit $ 4.03us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
$ 2.97us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
$ 1.69us-gaap_ShareBasedCompensationSharesAuthorizedUnderStockOptionPlansExercisePriceRangeUpperRangeLimit
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
   
Issuance of common stock 291us-gaap_ProceedsFromIssuanceOfCommonStock
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
201us-gaap_ProceedsFromIssuanceOfCommonStock
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
138us-gaap_ProceedsFromIssuanceOfCommonStock
/ us-gaap_AwardTypeAxis
= lts_QualifiedEmployeeStockPurchasePlanMember
   
Plan 1999 [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares available for grant 1,194,854us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= lts_Plan1999Member
       
Granted     500,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= lts_Plan1999Member
   
Options, outstanding, number 15,786,001us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= lts_Plan1999Member
16,932,401us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= lts_Plan1999Member
17,302,468us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= lts_Plan1999Member
17,765,468us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= lts_Plan1999Member
 
Plan 1999 [Member] | Maximum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Granted 25,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= lts_Plan1999Member
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
       
Awards with annual limit 1,500,000lts_AwardsWithAnnualLimit
/ us-gaap_AwardTypeAxis
= lts_Plan1999Member
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
       
Plan 2009 [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares available for grant 22,929,061us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
       
Granted 3,641,212us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
2,788,212us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
3,725,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
   
Awards with annual limit 1,500,000,000lts_AwardsWithAnnualLimit
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
       
Combined voting power 10.00%lts_SharebasedCompensationArrangementbySharebasedPaymentAwardCombinedVotingPower
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
       
Fair market value 100.00%lts_SharebasedCompensationArrangementbySharebasedPaymentAwardFairMarketValue
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
       
Fair market value for ten percent shareholder 110.00%lts_SharebasedCompensationArrangementbySharebasedPaymentAwardFairMarketValueforTenPercentShareholder
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
       
Options, outstanding, number 20,379,199us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
18,145,564us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
15,937,715us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
12,503,994us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsOutstandingNumber
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
 
Plan 2009 [Member] | Maximum          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Granted 45,000,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodGross
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
/ us-gaap_RangeAxis
= us-gaap_MaximumMember
       
Plan 2009 [Member] | Restricted Stock [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Number of shares available for grant 14,409us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
/ us-gaap_PlanNameAxis
= us-gaap_RestrictedStockMember
      200,000us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardNumberOfSharesAvailableForGrant
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
/ us-gaap_PlanNameAxis
= us-gaap_RestrictedStockMember
Equity instruments other than options, forfeited in period     12,500us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardEquityInstrumentsOtherThanOptionsForfeitedInPeriod
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
/ us-gaap_PlanNameAxis
= us-gaap_RestrictedStockMember
   
Allocated share-based compensation expense $ 2us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
/ us-gaap_PlanNameAxis
= us-gaap_RestrictedStockMember
  $ 54us-gaap_AllocatedShareBasedCompensationExpense
/ us-gaap_AwardTypeAxis
= lts_Plan2009Member
/ us-gaap_PlanNameAxis
= us-gaap_RestrictedStockMember
   
Employees and Director Option [Member]          
Share-based Compensation Arrangement by Share-based Payment Award [Line Items]          
Options, grants in period, weighted average grant date fair value $ 1.85us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= lts_EmployeesAndDirectorOptionMember
$ 0.74us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= lts_EmployeesAndDirectorOptionMember
$ 1.13us-gaap_ShareBasedCompensationArrangementByShareBasedPaymentAwardOptionsGrantsInPeriodWeightedAverageGrantDateFairValue
/ us-gaap_AwardTypeAxis
= lts_EmployeesAndDirectorOptionMember