Deposits and Borrowings - Long-Term Debt (Details) - USD ($) $ in Millions	Mar. 31, 2024	Dec. 31, 2023
Debt Instrument [Line Items]
Total long-term debt	$ 49,793	$ 49,318
Total short-term borrowings and long-term debt	50,361	49,856
Time deposits, at or above FDIC insurance limit	13,100	15,800
Deposit liability, uninsured	8,400	9,000
Senior and subordinated notes	32,108	31,248
Euro
Debt Instrument [Line Items]
Senior and subordinated notes	$ 1,300	1,300
Securitized debt obligations
Debt Instrument [Line Items]
Weighted-Average Interest Rate	3.00%
Carrying value	$ 17,661	18,043
Total senior and subordinated notes
Debt Instrument [Line Items]
Carrying value	$ 32,108	31,248
Senior notes \| Total unsecured senior debt
Debt Instrument [Line Items]
Weighted-Average Interest Rate	4.60%
Carrying value	$ 28,412	27,517
Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Weighted-Average Interest Rate	4.57%
Carrying value	$ 28,063	27,168
Senior notes \| Floating unsecured senior debt
Debt Instrument [Line Items]
Stated Interest Rates	6.68%
Weighted-Average Interest Rate	6.68%
Carrying value	$ 349	349
Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Weighted-Average Interest Rate	3.57%
Carrying value	$ 3,696	3,731
Other long-term borrowings
Debt Instrument [Line Items]
Weighted-Average Interest Rate	6.64%
Carrying value	$ 24	$ 27
Minimum \| Securitized debt obligations
Debt Instrument [Line Items]
Stated Interest Rates	0.55%
Minimum \| Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Stated Interest Rates	0.80%
Minimum \| Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Stated Interest Rates	2.36%
Minimum \| Other long-term borrowings
Debt Instrument [Line Items]
Stated Interest Rates	0.49%
Maximum \| Securitized debt obligations
Debt Instrument [Line Items]
Stated Interest Rates	6.13%
Maximum \| Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Stated Interest Rates	7.62%
Maximum \| Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Stated Interest Rates	4.20%
Maximum \| Other long-term borrowings
Debt Instrument [Line Items]
Stated Interest Rates	9.91%

Amount of short-term and long-term debt and lease obligation.

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