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, 2025	Dec. 31, 2024
Receivables from broker-dealers, clearing organizations and customers:
Securities failed-to-deliver - broker-dealers and clearing organizations	$ 184,441	$ 109,307
Securities failed-to-deliver - customers	297,606	136,424
Cash deposits with clearing organizations and broker-dealers	119,942	107,652
Other	4,678	4,345
Total	606,667	357,728
Payables to broker-dealers, clearing organizations and customers:
Securities failed-to-receive - broker-dealers and clearing organizations	254,622	158,694
Securities failed-to-receive - customers	101,514	51,916
Other	9,692	8,235
Total	$ 365,828	$ 218,845