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

The estimated net amount of existing gains or losses on cash flow hedges at the reporting date expected to be reclassified to earnings within the next 12 months.

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Aggregate net gain (loss) on all derivative instruments recognized in earnings during the period, before tax effects.

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Amount, after tax and before reclassification, of gain (loss) from derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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Amount, after tax, of reclassification of gain (loss) from accumulated other comprehensive income (AOCI) for derivative instrument designated and qualifying as cash flow hedge included in assessment of hedge effectiveness.

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