Receivables from and Payables to Broker-Dealers, Clearing Organizations, Customers and Related Broker-Dealers (Detail) - USD ($) $ in Thousands	Jun. 30, 2015	Dec. 31, 2014
Receivables from broker-dealers, clearing organizations, customers and related broker-dealers:
Contract values of fails to deliver	$ 963,667	$ 559,142
Receivables from clearing organizations	130,548	60,300
Other receivables from broker-dealers and customers	21,172	16,927
Net pending trades	427	884
Open derivative contracts	3,998	3,508
Total	1,119,812	640,761
Payables to broker-dealers, clearing organizations, customers and related broker-dealers:
Contract values of fails to receive	892,464	552,790
Payables to clearing organizations	57,909	79,848
Other payables to broker-dealers and customers	25,655	13,378
Open derivative contracts	1,607	153
Total	$ 977,635	$ 646,169