Financial Derivatives (Gains (Losses) Recognized on Fair Value and Cash Flow Hedges in the Consolidated Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended
Mar. 31, 2021	Mar. 31, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Loans	$ 1,996	$ 2,480
Investment Securities	421	582
Borrowed Funds	95	314
Noninterest income	1,872	1,825
Other
Derivative Instruments, Gain (Loss) [Line Items]
Noninterest income	483	343
Fair value hedges \| Designated as Hedging Instrument \| Investment Securities \| Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items	(8)	234
Derivatives	9	(231)
Amounts related to interest settlements on derivatives	(1)	(2)
Fair value hedges \| Designated as Hedging Instrument \| Borrowed Funds \| Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items	646	(1,361)
Derivatives	(664)	1,339
Amounts related to interest settlements on derivatives	134	59
Cash flow hedges \| Designated as Hedging Instrument \| Loans \| Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from AOCI	100	42
Cash flow hedges \| Designated as Hedging Instrument \| Investment Securities \| Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from AOCI	22	2
Cash flow hedges \| Designated as Hedging Instrument \| Other \| Noninterest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from AOCI	$ 13	$ 1

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Amount of the increase (decrease) in fair value of the hedged item in a fair value hedge recognized in the income statement.

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Amount of increase (decrease) in the fair value of derivatives recognized in the income statement.

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