Short-Term Borrowings (Summary of Short-Term Borrowings) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Year-end balance	$ 4,379	$ 10,417
Securities sold, not yet purchased	65	187
Total federal funds and other short-term borrowings	4,379	10,417
Other liabilities	1,585	1,871
Federal Home Loan Bank advances
Short-term Debt [Line Items]
Average amount outstanding	$ 4,208	$ 1,257
Average rate	5.73%	3.67%
Highest month-end balance	$ 11,525	$ 7,100
Year-end balance	$ 1,525	$ 7,100
Average rate on outstanding advances at year-end	5.59%	4.43%
Total federal funds and other short-term borrowings	$ 1,525	$ 7,100
Federal funds purchased
Short-term Debt [Line Items]
Other short-term borrowings, year-end balances	597	232
Security repurchase agreements
Short-term Debt [Line Items]
Other short-term borrowings, year-end balances	1,814	2,898
Swap Margin Collateral
Short-term Debt [Line Items]
Other short-term borrowings, year-end balances	$ 378	$ 0
Swap margin collateral		368 million