Annual report pursuant to Section 13 and 15(d)

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

v3.6.0.2
Intangible Assets (Intangible Assets Subject To Amortization) (Detail) - USD ($)
$ in Thousands
 12 Months Ended
Dec. 31, 2016
Dec. 31, 2015
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 9 years 9 months 29 days  
Gross Carrying Amount $ 217,550 $ 209,840
Accumulated Amortization $ 92,612 71,909
Technology    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 7 years 10 months 24 days  
Gross Carrying Amount $ 25,563 25,563
Accumulated Amortization $ 15,754 12,488
Relationships with financial advisors    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 15 years 6 months  
Gross Carrying Amount $ 117,995 110,671
Accumulated Amortization $ 40,505 32,028
Vendor relationships    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 7 years  
Gross Carrying Amount $ 3,613 3,613
Accumulated Amortization $ 3,613 3,613
Covenants not-to-compete    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 3 years 10 months 24 days  
Gross Carrying Amount $ 6,421 6,035
Accumulated Amortization $ 4,638 3,347
Customer accounts    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 8 years 3 months 18 days  
Gross Carrying Amount $ 2,029 2,029
Accumulated Amortization $ 1,971 1,765
Trade names    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 7 years 8 months 12 days  
Gross Carrying Amount $ 16,910 16,910
Accumulated Amortization $ 10,017 7,790
Renewal revenue    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 7 years 10 months 24 days  
Gross Carrying Amount $ 41,381 41,381
Accumulated Amortization $ 12,481 7,263
Relationships with investment banking clients    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 4 years  
Gross Carrying Amount $ 2,586 2,586
Accumulated Amortization $ 2,586 2,586
Leases    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 6 years  
Gross Carrying Amount $ 861 861
Accumulated Amortization $ 861 861
Referral agreement    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 6 years 7 months 6 days  
Gross Carrying Amount $ 124 124
Accumulated Amortization $ 119 101
Other    
Indefinite-lived Intangible Assets [Line Items]    
Weighted-Average Estimated Useful Life 6 years  
Gross Carrying Amount $ 67 67
Accumulated Amortization $ 67 $ 67