Quarterly report pursuant to Section 13 or 15(d)

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

v2.4.0.8
Off-Balance-Sheet Risk and Concentration of Credit Risk - Additional Information (Detail) (USD $)
In Thousands, unless otherwise specified
Sep. 30, 2014
Dec. 31, 2013
Off-Balance-Sheet Risk and Concentration of Credit Risk [Abstract]    
Receivables from clearing broker $ 68,378 $ 31,391