Derivatives - Derivatives Associated with Interest Rate Risk Management Activities (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Customer interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	$ 4,444	$ 4,096
Assets	26	8
Liabilities	108	190
Customer interest rate contracts | Customer Interest Rate Contracts Hedging  | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Notional	7,988	8,301
Assets	41	10
Liabilities	202	372
Offsetting upstream interest rate contracts
Derivative Instruments, Gain (Loss) [Line Items]
Notional	4,603	4,265
Assets	73	134
Liabilities	25	9
Offsetting upstream interest rate contracts | Customer Interest Rate Contracts Hedging  | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Notional	8,288	8,301
Assets	201	369
Liabilities	$ 42	$ 11