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, 2023	Dec. 31, 2022
Receivables from broker-dealers, clearing organizations and customers:
Securities failed-to-deliver - broker-dealers and clearing organizations	$ 195,727	$ 144,523
Securities failed-to-deliver - customers	232,892	235,056
Deposits with clearing organizations and broker-dealers	112,489	88,923
Other	6,973	7,833
Total	548,081	476,335
Payables to broker-dealers, clearing organizations and customers:
Securities failed-to-receive - broker-dealers and clearing organizations	151,639	224,816
Securities failed-to-receive - customers	206,387	71,828
Other	6,060	7,349
Total	$ 364,086	$ 303,993