Derivatives - Derivatives Associated with Cash Flow Hedges and Mortgage Banking Hedges (Details) - Hedging Instruments And Hedged Items - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Interest Rate Contract | Cash Flow Hedge
Derivative Instruments, Gain (Loss) [Line Items]
Variability in cash flows related to debt instruments (primarily loans)	$ 5,000	$ 5,000
Interest rate contracts | Cash Flow Hedge
Derivative Instruments, Gain (Loss) [Line Items]
Notional	5,000	5,000
Assets	0	0
Liabilities	15	67
Option contracts written | Mortgage Banking Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Notional	159	51
Assets	1	0
Liabilities	0	0
Forward contracts written | Mortgage Banking Hedges
Derivative Instruments, Gain (Loss) [Line Items]
Notional	169	100
Assets	0	1
Liabilities	$ 0	$ 0