Deposits and Borrowings - Long-Term Debt (Details) - USD ($) $ in Millions	Sep. 30, 2025	Dec. 31, 2024
Debt Instrument [Line Items]
Total long-term debt	$ 50,866	$ 44,989
Total short-term borrowings and long-term debt	51,482	45,551
Time deposits, at or above FDIC insurance limit	16,900	15,200
Deposit liability, uninsured	13,700	10,100
Senior and subordinated notes	36,662	30,696
Euro
Debt Instrument [Line Items]
Senior and subordinated notes	$ 543	473
Securitized debt obligations
Debt Instrument [Line Items]
Weighted-Average Interest Rate	3.78%
Carrying value	$ 13,642	14,264
Total senior and subordinated notes
Debt Instrument [Line Items]
Carrying value	$ 36,662	30,696
Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Weighted-Average Interest Rate	5.04%
Carrying value	$ 31,984	26,930
Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Weighted-Average Interest Rate	4.59%
Carrying value	$ 4,678	3,766
Total other long-term borrowings
Debt Instrument [Line Items]
Carrying value	$ 562	29
FHLB advances
Debt Instrument [Line Items]
Weighted-Average Interest Rate	4.82%
Carrying value	$ 538	0
Finance lease liabilities
Debt Instrument [Line Items]
Weighted-Average Interest Rate	5.64%
Carrying value	$ 24	$ 29
Minimum \| Securitized debt obligations
Debt Instrument [Line Items]
Stated Interest Rates	1.03%
Minimum \| Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Stated Interest Rates	1.65%
Minimum \| Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Stated Interest Rates	2.36%
Minimum \| FHLB advances
Debt Instrument [Line Items]
Stated Interest Rates	4.77%
Minimum \| Finance lease liabilities
Debt Instrument [Line Items]
Stated Interest Rates	3.74%
Maximum \| Securitized debt obligations
Debt Instrument [Line Items]
Stated Interest Rates	5.82%
Maximum \| Senior notes \| Fixed unsecured senior debt
Debt Instrument [Line Items]
Stated Interest Rates	7.96%
Maximum \| Subordinated notes \| Fixed unsecured subordinated debt
Debt Instrument [Line Items]
Stated Interest Rates	6.18%
Maximum \| FHLB advances
Debt Instrument [Line Items]
Stated Interest Rates	4.82%
Maximum \| Finance lease liabilities
Debt Instrument [Line Items]
Stated Interest Rates	9.91%

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

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