Derivative Instruments and Hedging Activities (Derivative Gain (Loss) Recognized/Reclassified) (Details) - USD ($) $ in Millions	3 Months Ended	6 Months Ended
Jun. 30, 2024	Jun. 30, 2023	Jun. 30, 2024	Jun. 30, 2023
Derivative Instruments, Gain (Loss) [Line Items]
Amount of gain/(loss) reclassified from AOCI into income	$ (23)	$ (30)	$ (49)	$ (67)
Loss to be reclassified within the next 12 months into interest income			88	106
Derivatives designated as hedging instruments:
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion of derivative gain/(loss) deferred in AOCI	0	(10)	(1)	28
Amount of gain/(loss) reclassified from AOCI into income	(31)	(40)	(65)	(89)
Interest on fair value hedges	22	0	43	10
Derivatives designated as hedging instruments: \| Cash Flow Hedging
Derivative Instruments, Gain (Loss) [Line Items]
Terminated or redesignated, unamortized basis adjustments, debt	43	50	43	50
Terminated or redesignated, unamortized basis adjustments, assets	3	3	3	3
Derivatives designated as hedging instruments: \| Cash Flow Hedging \| Receive-fixed interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion of derivative gain/(loss) deferred in AOCI	(1)	(21)	(6)	17
Amount of gain/(loss) reclassified from AOCI into income	(33)	(41)	(69)	(90)
Interest on fair value hedges	0	0	0	0
Derivatives designated as hedging instruments: \| Cash Flow Hedging \| Pay-fixed interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion of derivative gain/(loss) deferred in AOCI	1	11	5	11
Amount of gain/(loss) reclassified from AOCI into income	2	1	4	1
Interest on fair value hedges	0	0	0	0
Derivatives designated as hedging instruments: \| Fair Value Hedging \| Debt hedges: Receive-fixed interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion of derivative gain/(loss) deferred in AOCI	0	0	0	0
Amount of gain/(loss) reclassified from AOCI into income	0	0	0	0
Interest on fair value hedges	(2)	(9)	(3)	(6)
Derivatives designated as hedging instruments: \| Fair Value Hedging \| Asset hedges: Pay-fixed interest rate swaps
Derivative Instruments, Gain (Loss) [Line Items]
Effective portion of derivative gain/(loss) deferred in AOCI	0	0	0	0
Amount of gain/(loss) reclassified from AOCI into income	0	0	0	0
Interest on fair value hedges	$ 24	$ 9	$ 46	$ 16

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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Amount, before tax and reclassification, of gain (loss) from derivative instrument designated and qualifying 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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Terminated And Redesignated Swaps, Unamortized Basis Adjustments, Assets

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