Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers - Schedule of Receivables from and Payables to Broker-dealers, Clearing Organizations and Customers (Detail) - USD ($) $ in Thousands	Sep. 30, 2024	Dec. 31, 2023
Receivables from broker-dealers, clearing organizations and customers:
Securities failed-to-deliver - broker-dealers and clearing organizations	$ 121,943	$ 282,125
Securities failed-to-deliver - customers	240,629	284,322
Cash deposits with clearing organizations and broker-dealers	106,829	115,151
Other	5,588	6,338
Total	474,989	687,936
Payables to broker-dealers, clearing organizations and customers:
Securities failed-to-receive - broker-dealers and clearing organizations	207,297	125,022
Securities failed-to-receive - customers	68,321	405,186
Other	7,696	7,190
Total	$ 283,314	$ 537,398