Financial Derivatives (Gains (Losses) Recognized on Fair Value and Cash Flow Hedges in Consolidated Income Statement) (Details) - USD ($) $ in Millions	12 Months Ended
Dec. 31, 2020	Dec. 31, 2019	Dec. 31, 2018
Derivative Instruments, Gain (Loss) [Line Items]
Loans, interest income	$ 8,927	$ 10,525	$ 9,580
Investment securities, interest income	2,041	2,426	2,261
Borrowed funds, interest expense	718	1,811	1,632
Total noninterest income	6,955	6,874	6,469
Other
Derivative Instruments, Gain (Loss) [Line Items]
Total noninterest income	1,364	1,473	1,205
Fair Value Hedging \| Designated as Hedging Instrument \| Investment Securities \| Investment Securities Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on related hedged items recognized in income	208	187	(53)
Gain (loss) on derivatives recognized in income	(202)	(178)	60
Interest settlements on derivatives	(9)	13	3
Fair Value Hedging \| Designated as Hedging Instrument \| Borrowings \| Borrowed Funds Interest Expense
Derivative Instruments, Gain (Loss) [Line Items]
Gain (loss) on related hedged items recognized in income	(1,059)	(808)	151
Gain (loss) on derivatives recognized in income	959	659	(262)
Interest settlements on derivatives	480	79	80
Cash Flow Hedging \| Designated as Hedging Instrument \| Loans \| Investment Securities Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from AOCI	375	9	41
Cash Flow Hedging \| Designated as Hedging Instrument \| Investment Securities \| Investment Securities Interest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from AOCI	40	9	11
Cash Flow Hedging \| Designated as Hedging Instrument \| Other Income \| Noninterest Income
Derivative Instruments, Gain (Loss) [Line Items]
Amount of derivative gains (losses) reclassified from AOCI	$ 6	$ 19	$ 8

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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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