Basis of Presentation - Reconciliation of Cash and Cash Equivalents (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024	Sep. 30, 2024	Dec. 31, 2023
Organization, Consolidation and Presentation of Financial Statements [Abstract]
Cash and cash equivalents	$ 1,235	$ 611	$ 784
Restricted cash and restricted cash equivalents (included in segregated cash and investments)	4,640		3,613
Total cash, cash equivalents, restricted cash, and restricted cash equivalents	$ 5,875	$ 3,924	$ 4,397	$ 5,390