Derivatives - Gains/(Losses) on Derivatives Associated with Cash Flow Hedges and Mortgage Banking Hedges (Details) - USD ($) $ in Millions	3 Months Ended
	Mar. 31, 2026	Mar. 31, 2025
Derivative Instruments, Gain (Loss) [Line Items]
Loss expected to be reclassified to earnings in the next twelve months	$ 17	$ 17
Cash Flow Hedge | Hedging Instruments and Hedged Items:
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss), cash flow hedges	(16)	18
Gain (loss) reclassified from AOCI into interest income	6	9
Interest rate contracts | Cash Flow Hedge | Hedging Instruments and Hedged Items:
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses), cash flow hedges	(14)	36
Option contracts written | Mortgage Banking Hedges | Hedging Instruments and Hedged Items:
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivative instruments	1	(1)
Forward contracts written | Mortgage Banking Hedges | Hedging Instruments and Hedged Items:
Derivative Instruments, Gain (Loss) [Line Items]
Gains (losses) on derivative instruments	$ (2)	$ 1