Derivative Financial Instruments - Amounts Related to Cash Flow Hedges (Details) - Cash Flow Hedges - Interest Rate Contracts - USD ($) $ in Millions	3 Months Ended		6 Months Ended
	Jun. 30, 2022	Jun. 30, 2021	Jun. 30, 2022	Jun. 30, 2021
Interest Expense
Derivative Instruments, Notional, Fair Value Assets and Liabilities[Line Items]
Pre-tax gain (loss) reclassified from AOCI into expense	$ (5)	$ (13)	$ (11)	$ (24)
Other Expense
Derivative Instruments, Notional, Fair Value Assets and Liabilities[Line Items]
Pre-tax gain (loss) reclassified from AOCI into expense	0	0	0	(36)	[1]
Commercial loans
Derivative Instruments, Notional, Fair Value Assets and Liabilities[Line Items]
Pre-tax gain (loss) recognized in OCI	59	0	59	0
Deposits | Interest Expense
Derivative Instruments, Notional, Fair Value Assets and Liabilities[Line Items]
Pre-tax gain (loss) reclassified from AOCI into expense	0	(1)	0	(2)
Deposits | Other Expense
Derivative Instruments, Notional, Fair Value Assets and Liabilities[Line Items]
Pre-tax gain (loss) reclassified from AOCI into expense	0	0	0	(12)	[1]
Short-term Debt | Interest Expense
Derivative Instruments, Notional, Fair Value Assets and Liabilities[Line Items]
Pre-tax gain (loss) reclassified from AOCI into expense	0	(7)	0	(12)
Short-term Debt | Other Expense
Derivative Instruments, Notional, Fair Value Assets and Liabilities[Line Items]
Pre-tax gain (loss) reclassified from AOCI into expense	0	0	0	(20)	[1]
Long-term debt | Interest Expense
Derivative Instruments, Notional, Fair Value Assets and Liabilities[Line Items]
Pre-tax gain (loss) reclassified from AOCI into expense	(5)	(5)	(11)	(10)
Long-term debt | Other Expense
Derivative Instruments, Notional, Fair Value Assets and Liabilities[Line Items]
Pre-tax gain (loss) reclassified from AOCI into expense	$ 0	$ 0	$ 0	$ (4)	[1]

[1] Represents the accelerated amortization of amounts reclassified from AOCI, where management determined that the forecasted transaction is probable of not occurring.