Derivatives - Gains/(Losses) on Derivatives Associated with Cash Flow Hedges and Mortgage Banking Hedges (Details) - USD ($) $ in Millions	3 Months Ended		9 Months Ended
	Sep. 30, 2025	Sep. 30, 2024	Sep. 30, 2025	Sep. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Loss expected to be reclassified to earnings in the next twelve months	$ (7)	$ (7)	$ (7)	$ (7)
Cash Flow Hedge | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses), cash flow hedges	(4)	45	21	(13)
Gain (loss) reclassified from AOCI into interest income	9	13	27	39
Interest rate contracts | Cash Flow Hedge | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses), cash flow hedges	7	77	64	35
Option contracts written | Mortgage Banking Hedges | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivative instruments	0	0	0	0
Forward contracts written | Mortgage Banking Hedges | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivative instruments	$ 1	$ 3	$ 0	$ (5)