Financial Instruments Subject to Off-Balance Sheet Credit Risk - Summary of the Fair Value of Client Securities Available to Utilize as Collateral and Amounts Pledged (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Securities Financing Transaction [Line Items]
Fair value of client securities available to be pledged	$ 94,483	$ 86,911
Total collateral pledged to third parties	28,753	27,043
Fulfillment of requirements with the Options Clearing Corporation
Securities Financing Transaction [Line Items]
Total collateral pledged to third parties	16,803	13,355
Fulfillment of client short sales
Securities Financing Transaction [Line Items]
Total collateral pledged to third parties	5,987	7,009
Securities lending to other broker-dealers
Securities Financing Transaction [Line Items]
Total collateral pledged to third parties	5,029	4,688
Collateral for secured short-term borrowings
Securities Financing Transaction [Line Items]
Total collateral pledged to third parties	934	1,991
Fully Paid Client Securities
Securities Financing Transaction [Line Items]
Total collateral pledged to third parties	$ 229	$ 179