Cash, Cash Equivalents, and Cash Restricted for Regulatory Purposes for Periods Presented in Consolidated Statements of Financial Condition - USD ($) $ in Thousands	Sep. 30, 2023	Dec. 31, 2022	Sep. 30, 2022	Dec. 31, 2021
Statement of Cash Flows [Abstract]
Cash and cash equivalents	$ 2,768,353	$ 2,199,985
Cash segregated for regulatory purposes	33,399	29,017
Total cash, cash equivalents, and cash segregated for regulatory purposes	$ 2,801,752	$ 2,229,002	$ 1,446,412	$ 2,149,657