Annual report pursuant to Section 13 and 15(d)

Intangible Assets (Intangible Assets Subject To Amortization) (Detail)

v2.4.1.9
Intangible Assets (Intangible Assets Subject To Amortization) (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 8 years 2 months 19 days  
Gross Carrying Amount $ 174,259us-gaap_FiniteLivedIntangibleAssetsGross $ 113,453us-gaap_FiniteLivedIntangibleAssetsGross
Accumulated Amortization 51,258us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization 37,202us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
Technology    
Indefinite-lived Intangible Assets [Line Items]    
Gross Carrying Amount 23,483us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_TechnologyMember
21,422us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_TechnologyMember
Accumulated Amortization 9,223us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_TechnologyMember
6,359us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_TechnologyMember
Technology | Minimum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 1 year  
Technology | Maximum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 7 years 8 months 12 days  
Relationships With Financial Advisors    
Indefinite-lived Intangible Assets [Line Items]    
Gross Carrying Amount 81,438us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RelationshipsWithFinancialAdvisorsMember
68,688us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RelationshipsWithFinancialAdvisorsMember
Accumulated Amortization 23,704us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RelationshipsWithFinancialAdvisorsMember
17,554us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RelationshipsWithFinancialAdvisorsMember
Relationships With Financial Advisors | Minimum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 9 years 2 months 12 days  
Relationships With Financial Advisors | Maximum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 20 years  
Relationships With Financial Advisors | Weighted Average    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 10 years 2 months 12 days  
Vendor Relationship    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 7 years  
Gross Carrying Amount 3,613us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_VendorRelationshipMember
3,613us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_VendorRelationshipMember
Accumulated Amortization 3,458us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_VendorRelationshipMember
2,998us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_VendorRelationshipMember
Covenants Not-to-Compete    
Indefinite-lived Intangible Assets [Line Items]    
Gross Carrying Amount 5,401us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_CovenantsNotToCompeteMember
1,773us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_CovenantsNotToCompeteMember
Accumulated Amortization 2,100us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_CovenantsNotToCompeteMember
1,735us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_CovenantsNotToCompeteMember
Covenants Not-to-Compete | Minimum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 2 years 2 months 12 days  
Covenants Not-to-Compete | Maximum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 5 years  
Customer Account    
Indefinite-lived Intangible Assets [Line Items]    
Gross Carrying Amount 2,029us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_CustomerAccountMember
2,029us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_CustomerAccountMember
Accumulated Amortization 1,516us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_CustomerAccountMember
1,266us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_CustomerAccountMember
Customer Account | Minimum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 6 years 10 months 24 days  
Customer Account | Maximum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 10 years  
Renewal revenue    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 7 years 9 months 18 days  
Gross Carrying Amount 39,503us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RenewalsRevenueMember
0us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RenewalsRevenueMember
Accumulated Amortization 5,563us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RenewalsRevenueMember
0us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RenewalsRevenueMember
Trade names    
Indefinite-lived Intangible Assets [Line Items]    
Gross Carrying Amount 15,154us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TradeNamesMember
12,290us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TradeNamesMember
Accumulated Amortization 2,099us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TradeNamesMember
3,716us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_TradeNamesMember
Trade names | Minimum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 7 years 2 months 12 days  
Trade names | Maximum    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 10 years  
Trade names | Weighted Average    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 9 years  
Relationships With Investment Banking Clients    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 4 years  
Gross Carrying Amount 2,586us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RelationshipsWithInvestmentBankingClientsMember
2,586us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RelationshipsWithInvestmentBankingClientsMember
Accumulated Amortization 2,586us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RelationshipsWithInvestmentBankingClientsMember
2,586us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_RelationshipsWithInvestmentBankingClientsMember
Leases    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 6 years 4 months 24 days  
Gross Carrying Amount 861us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_LeasesMember
861us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_LeasesMember
Accumulated Amortization 861us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_LeasesMember
861us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_LeasesMember
Referral Agreement    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 6 years 7 months 6 days  
Gross Carrying Amount 124us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_ReferralAgreementMember
124us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_ReferralAgreementMember
Accumulated Amortization 81us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_ReferralAgreementMember
64us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= lts_ReferralAgreementMember
Other    
Indefinite-lived Intangible Assets [Line Items]    
Estimated useful life 6 years  
Gross Carrying Amount 67us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_OtherCreditDerivativesMember
67us-gaap_FiniteLivedIntangibleAssetsGross
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_OtherCreditDerivativesMember
Accumulated Amortization $ 67us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_OtherCreditDerivativesMember
$ 63us-gaap_FiniteLivedIntangibleAssetsAccumulatedAmortization
/ us-gaap_IndefiniteLivedIntangibleAssetsByMajorClassAxis
= us-gaap_OtherCreditDerivativesMember