Receivable from and Payable to Brokers, Dealers and Clearing Organizations (Details) - USD ($) $ in Thousands	Sep. 30, 2016	Dec. 31, 2015
Receivable:
Clearing organizations and other	$ 458,972	$ 505,789
Financial instruments purchased under agreement to resell	59,980	65,433
Securities failed to deliver	177,543	109,989
Total receivable	696,495	681,211
Payable:
Clearing organizations and other	559,621	240,985
Securities failed to receive	87,468	32,820
Total payable	$ 647,089	$ 273,805