Financial Derivatives (Gains (Losses) Recognized on Fair Value and Cash Flow Hedges in the Consolidated Income Statement) (Details) - USD ($) $ in Millions	3 Months Ended	9 Months Ended
Sep. 30, 2021	Sep. 30, 2020	Sep. 30, 2021	Sep. 30, 2020
Derivative Instruments, Gain (Loss) [Line Items]
Loans	$ 2,437	$ 2,116	$ 6,593	$ 6,853
Investment Securities	460	490	1,350	1,599
Borrowed Funds	90	118	275	619
Noninterest income	2,341	1,797	6,299	5,171
Other
Derivative Instruments, Gain (Loss) [Line Items]
Noninterest income	449	457	1,400	1,071
Fair value hedges \| Designated as Hedging Instrument \| Investment Securities \| Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items	2	(13)	(3)	224
Derivatives		14	7	(219)
Amounts related to interest settlements on derivatives	(1)	(3)	(3)	(7)
Fair value hedges \| Designated as Hedging Instrument \| Borrowed Funds \| Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Hedged items	155	141	695	(1,300)
Derivatives	(169)	(166)	(740)	1,220
Amounts related to interest settlements on derivatives	129	149	394	341
Cash flow hedges \| Designated as Hedging Instrument \| Loans \| Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from AOCI	91	118	282	262
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	11	16	49	19
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		$ 27	$ 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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