Short-Term Borrowings - Summary of Short-Term Borrowings and Weighted-Average Rates (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023
Short-term Debt [Line Items]
Federal funds purchased	$ 204	$ 193
Other short-term borrowings	4,450	2,861
Federal Funds Purchased
Short-term Debt [Line Items]
Short-term borrowings, average	207	307
Short-term borrowings, maximum month-end balance	$ 247	$ 1,143
Short-term borrowings, rate	4.30%	5.31%
Short-term borrowings, average rate	5.21%	4.96%
Other Short Term Borrowings
Short-term Debt [Line Items]
Short-term borrowings, average	$ 3,024	$ 5,044
Short-term borrowings, maximum month-end balance	$ 5,070	$ 7,423
Short-term borrowings, rate	4.39%	5.21%
Short-term borrowings, average rate	5.18%	4.90%