Annual report pursuant to Section 13 and 15(d)

Goodwill (Changes To The Carrying Amount) (Detail)

v2.4.1.9
Goodwill (Changes To The Carrying Amount) (Detail) (USD $)
In Thousands, unless otherwise specified
12 Months Ended
Dec. 31, 2014
Dec. 31, 2013
Dec. 31, 2012
Goodwill [Roll Forward]      
Beginning balance $ 90,501us-gaap_Goodwill $ 90,578us-gaap_Goodwill  
Benefit applied to reduce goodwill (68)lts_BenefitAppliedToReduceGoodwill (77)lts_BenefitAppliedToReduceGoodwill (71)lts_BenefitAppliedToReduceGoodwill
Business acquisitions 24,805us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates    
Ending balance 115,238us-gaap_Goodwill 90,501us-gaap_Goodwill 90,578us-gaap_Goodwill
Ladenburg      
Goodwill [Roll Forward]      
Beginning balance 301us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_LadenburgThalmannAndCoIncMember
301us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_LadenburgThalmannAndCoIncMember
 
Benefit applied to reduce goodwill 0lts_BenefitAppliedToReduceGoodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_LadenburgThalmannAndCoIncMember
0lts_BenefitAppliedToReduceGoodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_LadenburgThalmannAndCoIncMember
 
Business acquisitions 0us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_LadenburgThalmannAndCoIncMember
   
Ending balance 301us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_LadenburgThalmannAndCoIncMember
301us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_LadenburgThalmannAndCoIncMember
 
Independent brokerage and advisory services      
Goodwill [Roll Forward]      
Beginning balance 90,200us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_IndependentBrokerageAndAdvisoryServicesMember
90,277us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_IndependentBrokerageAndAdvisoryServicesMember
 
Benefit applied to reduce goodwill (68)lts_BenefitAppliedToReduceGoodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_IndependentBrokerageAndAdvisoryServicesMember
(77)lts_BenefitAppliedToReduceGoodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_IndependentBrokerageAndAdvisoryServicesMember
 
Business acquisitions 13,290us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_IndependentBrokerageAndAdvisoryServicesMember
   
Ending balance 103,422us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_IndependentBrokerageAndAdvisoryServicesMember
90,200us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_IndependentBrokerageAndAdvisoryServicesMember
 
Insurance Brokerage [Member]      
Goodwill [Roll Forward]      
Beginning balance 0us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_InsuranceBrokerageMember
0us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_InsuranceBrokerageMember
 
Benefit applied to reduce goodwill 0lts_BenefitAppliedToReduceGoodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_InsuranceBrokerageMember
0lts_BenefitAppliedToReduceGoodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_InsuranceBrokerageMember
 
Business acquisitions 11,515us-gaap_PaymentsToAcquireInterestInSubsidiariesAndAffiliates
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_InsuranceBrokerageMember
   
Ending balance $ 11,515us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_InsuranceBrokerageMember
$ 0us-gaap_Goodwill
/ us-gaap_RelatedPartyTransactionsByRelatedPartyAxis
= lts_InsuranceBrokerageMember