Quarterly report pursuant to Section 13 or 15(d)

Off-Balance-Sheet Risk and Concentration of Credit Risk - Additional Information (Detail)

v2.4.1.9
Off-Balance-Sheet Risk and Concentration of Credit Risk - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
Mar. 31, 2015
Dec. 31, 2014
Off-Balance-Sheet Risk and Concentration of Credit Risk [Abstract]    
Receivables from clearing broker $ 45,618us-gaap_ReceivablesFromClearingOrganizations $ 38,760us-gaap_ReceivablesFromClearingOrganizations