Pledged Assets, Accepted Collateral and Restricted Assets (Narrative) (Details) - USD ($)	6 Months Ended	12 Months Ended
	Jun. 30, 2026	Dec. 31, 2025
Financial Instruments Owned and Pledged as Collateral [Line Items]
Cash, held in foreign currency	$ 1,900,000,000	$ 1,800,000,000
Restricted cash	526,700,000	531,200,000
Average deposits maintained to meet Federal Reserve Bank reserve requirements	0	0
Debt Securities And Loans
Financial Instruments Owned and Pledged as Collateral [Line Items]
Collateral that may be repledged or sold	$ 1,800,000,000	$ 1,000,000,000.0