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	Jun. 30, 2026	Dec. 31, 2025
Receivables from broker-dealers, clearing organizations and customers:
Securities failed-to-deliver - broker-dealers and clearing organizations	$ 500,597	$ 244,405
Securities failed-to-deliver - customers	592,254	131,632
Cash deposits with clearing organizations and broker-dealers	122,677	107,223
Other	12,925	5,951
Total	1,228,453	489,211
Payables to broker-dealers, clearing organizations and customers:
Securities failed-to-receive - broker-dealers and clearing organizations	479,823	224,844
Securities failed-to-receive - customers	372,280	93,107
Other	11,443	8,008
Total	$ 863,546	$ 325,959