Derivatives - Gains/(Losses) on Derivatives Associated with Cash Flow Hedges and Mortgage Banking Hedges (Details) - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2025	Jun. 30, 2024	Jun. 30, 2025	Jun. 30, 2024
Derivative Instruments, Gain (Loss) [Line Items]
Loss expected to be reclassified to earnings in the next twelve months	$ (8)	$ (8)	$ (8)	$ (8)
Cash Flow Hedge | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses), cash flow hedges	7	(15)	25	(58)
Gain (loss) reclassified from AOCI into interest income	9	13	18	26
Interest rate contracts | Cash Flow Hedge | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses), cash flow hedges	21	(2)	57	(41)
Option contracts written | Mortgage Banking Hedges | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivative instruments	0	1	(1)	0
Forward contracts written | Mortgage Banking Hedges | Hedging Instruments And Hedged Items
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivative instruments	$ 0	$ 0	$ (2)	$ 1