Short-Term Borrowings - Schedule of Short-term Borrowings (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2025	Dec. 31, 2024	Dec. 31, 2023
Short-term Debt [Line Items]
Year-end balance	$ 3,254	$ 3,400
Trading Liabilities
Short-term Debt [Line Items]
Average balance	644	555	$ 301
Year-end balance	607	550	509
Maximum month-end outstanding	$ 759	$ 767	$ 509
Average rate for the year	4.01%	4.22%	4.16%
Average rate at year-end	3.71%	4.20%	4.48%
Federal Funds Purchased
Short-term Debt [Line Items]
Average balance	$ 801	$ 420	$ 349
Year-end balance	1,039	259	302
Maximum month-end outstanding	$ 1,138	$ 626	$ 622
Average rate for the year	4.32%	5.34%	5.12%
Average rate at year-end	3.67%	4.40%	5.40%
Securities Sold Under Agreements to Repurchase
Short-term Debt [Line Items]
Average balance	$ 1,853	$ 1,720	$ 1,426
Year-end balance	1,973	2,096	1,921
Maximum month-end outstanding	$ 2,205	$ 2,096	$ 1,957
Average rate for the year	3.07%	3.83%	3.66%
Average rate at year-end	2.53%	3.23%	3.98%
Other Short-term Borrowings
Short-term Debt [Line Items]
Average balance	$ 685	$ 781	$ 2,688
Year-end balance	242	1,045	326
Maximum month-end outstanding	$ 2,636	$ 2,067	$ 7,476
Average rate for the year	4.37%	5.38%	5.19%
Average rate at year-end	3.81%	4.48%	5.36%