Pledged Assets, Accepted Collateral and Restricted Assets (Type of Pledged Assets) (Details) - Collateral that may be repledged or sold - USD ($) $ in Billions	Mar. 31, 2026	Dec. 31, 2025
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	$ 41.5	$ 42.4
Debt Securities
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	32.3	33.0
Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Total Pledged Assets	$ 9.2	$ 9.4