Short-Term Borrowings - Components of Short-Term Borrowings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2024	Dec. 31, 2023	Dec. 31, 2022
Short-term Debt [Line Items]
Balance at year end, securities sold under repurchase agreements	$ 0	$ 0
FEDERAL FUNDS PURCHASED
Short-term Debt [Line Items]
Balance at year end, federal funds purchase	0	0	$ 4,006
Average during the year	67	1,098	1,490
Maximum month-end balance	$ 0	$ 3,020	$ 5,872
Weighted-average rate during the year	5.29%	4.83%	2.04%
Weighted-average rate at year end	0.00%	0.00%	4.18%
SECURITIES SOLD UNDER REPURCHASE AGREEMENTS
Short-term Debt [Line Items]
Average during the year	$ 36	$ 549	$ 617
Maximum month-end balance	$ 44	$ 1,954	$ 1,090
Weighted-average rate during the year	2.61%	4.77%	1.66%
Weighted-average rate at year end	3.15%	1.63%	3.74%
Balance at year end, securities sold under repurchase agreements	$ 14	$ 38	$ 71
OTHER SHORT-TERM BORROWINGS
Short-term Debt [Line Items]
Average during the year	2,984	5,890	2,963
Maximum month-end balance	$ 6,794	$ 1,061	$ 11,372
Weighted-average rate during the year	5.49%	5.24%	1.82%
Weighted-average rate at year end	4.95%	5.58%	0.50%
Balance at year end, other short-term borrowings	$ 2,130	$ 3,053	$ 5,386